THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 

PRESENTED  BY 

PROF.  CHARLES  A.  KOFOID  AND 
MRS.  PRUDENCE  W.  KOFOID 


THE  SCIENCE  SERIES 


1.  The  Study  of  Man.  By  A.  C.  H ADDON.  Illustrated.  8° 

2.  The   Groundwork  of  Science.     By  ST.  GEORGE  Mi- 

VART. 

3.  Rivers  of  North  America.      By  ISRAEL  C.  RUSSELL. 

Illustrated. 

4.  Earth   Sculpture  ;  or,  The  Origin  of  Land  Forms. 

By  JAMES  GEIKIE.     Illustrated. 

5.  Volcanoes;  Their  Structure  and  Significance.     By 

T.  G.  BONNEY.     Illustrated. 

6.  Bacteria.     By  GEORGE  NEWMAN.     Illustrated. 

7.  A  Book  of  Whales.     By  F.  E.  BEDDARD.    Illustrated. 

8.  Comparative  Physiology    of  the    Brain,    etc.       By 

JACQUES  LOEB.     Illustrated. 

9.  The  Stars.     By  SIMON  NEWCOMB.     Illustrated. 

10.  The  Basis  of  Social  Relations.  By  DANIEL  G.  BRINTON. 
xi.  Experiments  on  Animals.     By  STEPHEN  PAGET. 

12.  Infection  and  Immunity.     By  GEORGE  M.  STERNBERG. 


For  list  of  works  in  preparation  see  end  of  this  volume. 


ITbe  Science  Series 

EDITED    BY 

professor  3.  Acfteen  Cattell,  flD.H.,  pb.S). 

AND 

jf .  £. 


INFECTION  AND   IMMUNITY 


Infection  and  Immunity 

With  Special  Reference  to 

The  Prevention  of  Infectious 
Diseases 


By 

George  M.  Sternberg,  M.D.,  LL.D. 

Surgeon- General  U.  S.  Army  (Retired) 

Ex-President  of  the  American  Medical  Association,  and  of  the  American  Public 

Health  Association  ;   Honorary  Member  of  the  Epidemiological  Society 

of  London,  of  the  Societe*  Francaise  d'Hygiene,  of  the 

Royal  Academy  of  Medicine  of  Rome,  etc. 


G.  P.  Putnam's  Sons 

New  York  and  London 

Cbc  fsntcherbocfcer  pre$3 

1903 


COPYRIGHT,  1903 

BY 
G.  P.  PUTNAM'S  SONS 


Published,  October,  1903 


Ubc  Untcherbocfeer  preee,  f*ew 


PREFACE 

I N  this  volume  the  writer  has  attempted  to  state  the 
main  facts,  so  far  as  they  have  been  established, 
with  reference  to  infection  and  immunity,  with  the 
practical  object  in  view  of  indicating  the  measures 
necessary  for  the  prevention  of  infectious  diseases. 
As  the  work  is  intended  for  non-medical  readers,  I 
have  avoided  technical  terms  as  far  as  practicable,  and 
when  it  has  been  necessary  to  use  these  have  endeav- 
oured to  explain  them.  I  have  thought  it  best  not 
to  enter  upon  a  discussion  of  the  theories  of  im- 
munity, or  to  attempt  to  give  an  account  of  the  re- 
sults of  recent  investigations  with  reference  to  the 
"  antitoxins,"  "  agglutinins,"  "  precipitins,"  "  bacterio- 
lysins,"  etc.  This  line  of  investigation  has,  during 
the  past  few  years,  been  so  prolific  in  surprising  re- 
sults, and  so  many  new  technical  terms  have  become 
necessary  for  the  designation  of  the  newly  discovered 
bodies  of  this  class  and  for  the  understanding  of 
Ehrlich's  "  side-chain  theory,"  which  attempts  to  ex- 
plain their  mode  of  action,  that  this  subject  does  not, 

iii 

1KS63B18 


iv  PREFACE 

at  present,  seem  suitable  for  popular  treatment.  In 
my  opinion,  a  knowledge  of  the  well  established  facts 
in  this  field  of  investigation  should  constitute  an  es- 
sential part  of  a  liberal  education  ;  and  the  diffusion 
of  such  knowledge  cannot  fail  to  promote  the  sanitary 
interests  of  the  people. 

The  general  statement  may  be  made  that  all  infec- 
tious diseases  are  preventable  diseases,  and  at  the 
present  time  it  is  possible  to  indicate  the  necessary 
measures  of  prevention  for  nearly  all  of  these  dis- 
eases. That  they  continue  to  prevail,  and  to  claim 
hundreds  of  thousands  of  victims  annually,  is  largely 
due  to  the  fact  that  the  public,  generally,  has  not  yet 
been  educated  upon  these  subjects. 

It  would  seem  that  so  important  a  matter  should 
receive  special  attention  in  our  high  schools  and  col- 
leges, and  the  writer  hopes  that  this  volume  may,  to 
some  extent  at  least,  serve  as  a  text-book,  suitable 
for  the  use  of  students,  and  as  a  manual  of  ready 
reference  for  those  who  are  responsible  for  the  sani- 
tary welfare  of  the  inmates  of  homes,  schools,  public 
institutions,  etc.  In  Part  Second  the  most  important 
infectious  diseases  are  considered  in  special  chapters, 
and  an  attempt  has  been  made  to  indicate  the  manner 
in  which  each  one  is  propagated,  its  importance  as  a 
factor  in  our  mortality  statistics,  and  the  best  methods 
of  restricting  its  extension.  I  have  been  strongly 


PREFACE  v 

tempted  to  write  an  additional  chapter  upon  venereal 
diseases,  but  have  refrained  from  treating  this  un- 
savoury topic.  I  may,  however,  be  permitted  to  quote 
here  from  the  concluding  paragraph  of  my  "  Lomb 
Prize  Essay,"  upon  Disinfection  and  Personal  Prophy- 
laxis against  Infectious  Diseases,  published  by  the 
American  Public  Health  Association  in  1886  : 

"  This  chapter  might  be  greatly  extended,  but,  having  passed 
in  review  the  principal  measures  of  individual  prophylaxis  against 
those  infectious  diseases  which  are  most  fatal,  we  shall  not  dwell 
upon  precautions  to  be  taken  in  other  contagious  diseases.  These 
precautions  will  not  differ  from  those  already  recommended  in 
the  cases  of  smallpox  and  scarlet  fever.  So,  too,  in  regard  to  the 
infectious  skin  diseases.  These  are  communicated  by  personal 
contact,  and  rarely  occur  except  among  those  who  neglect  per- 
sonal cleanliness  as  well  as  other  sanitary  laws.  Soap  and  water 
will  generally  suffice  for  individual  prophylaxis.  By  avoiding 
filthy  persons  as  well  as  filthy  places,  the  danger  of  contracting 
these  and  certain  other  unmentionable  infectious  diseases  will  be 
reduced  to  a  minimum." 

G.  M.  S. 

2144  CALIFORNIA  AVENUE, 

WASHINGTON,  June  /o,  1903. 


CONTENTS 

PART  FIRST 
CHAPTER  I 

PAGE 

GENERAL  REMARKS  UPON  INFECTION        ...  3 

CHAPTER  II 
DISEASE  GERMS 

CHAPTER  III 

CHANNELS  OF  INFECTION 14 

CHAPTER  IV 
SUSCEPTIBILITY  TO  INFECTION 23 

CHAPTER  V 
DISINFECTION 28 

CHAPTER  VI 

TESTS  OF  DISINFECTION 32 

CHAPTER  VII 

DISINFECTION  BY  HEAT 43 

CHAPTER   VIII   • 

SUNLIGHT  AS  A  DISINFECTANT 48 

CHAPTER  IX 
DISINFECTION  BY  GASES 51 

CHAPTER  X 
VARIOUS  CHEMICAL  DISINFECTANTS 57 


viii  CONTENTS 

CHAPTER  XI  PAGE 

NATURAL  IMMUNITY 63 

CHAPTER  XII 

ACQUIRED  IMMUNITY 73 

CHAPTER  XIII 

ANTITOXINS 82 

PART  SECOND 
CHAPTER  I 

BUBONIC  PLAGUE 89 

CHAPTER  II 

ASIATIC  CHOLERA no 


CHAPTER  III 
TYPHOID  FEVER 126 

CHAPTER   IV 
DYSENTERY,  CHOLERA  INFANTUM,  ETC 140 

CHAPTER  V 

RELAPSING  FEVER 145 

CHAPTER  VI 
TYPHUS  FEVER 154 

CHAPTER  VII 

TUBERCULOSIS 159 

CHAPTER   VIII 
LEPROSY .181 

CHAPTER  IX 

DIPHTHERIA 191 

CHAPTER  X 

INFLUENZA 199 


PNEUMONIA 
WHOOPING-COUGH 
SMALLPOX 
SCARLET  FEVER 
MEASLES    . 
MALARIAL  FEVERS 
YELLOW  FEVER 
WOUND  INFECTIONS 
TETANUS  . 

HYDROPHOBIA   . 
INDEX 


CONTENTS 
CHAPTER  XI 

CHAPTER  XII 
CHAPTER  XIII 
CHAPTER  XIV 

CHAPTER  XV 

CHAPTER   XVI 

CHAPTER  XVII 

CHAPTER  XVIII 

CHAPTER  XIX 

CHAPTER   XX 


IX 

PAGE 
2O5 

211 
214 


228 
234 
252 
264 
272 

279 
289 


ILLUSTRATIONS 

FIGURE  PACK 

i. — BACILLUS  OF  BUBONIC  PLAGUE          ....  101 

2. — SPIRILLUM  OF  ASIATIC  CHOLERA  ("COMMA    BACIL- 
LUS OF  KOCH") 121 

3. — BACILLUS  OF  TYPHOID  FEVER 136 

4. — SPIRILLUM   OF   RELAPSING  FEVER,  AS  SEEN  IN  THE 

BLOOD 149 

5. — BACILLUS  OF  TUBERCULOSIS,  AS  SEEN  IN  THE  SPUTUM 

OF  A  PATIENT  HAVING  PULMONARY  CONSUMPTION  .  160 

6. — BACILLUS  OF  LEPROSY,  AS  SEEN  IN  A  THIN  SECTION 

OF  A  LEPROUS  NODULE *      .  182 

7. — BACILLUS  OF  DIPHTHERIA          .....  193 

8.— BACILLUS  OF  INFLUENZA 200 

9. — MICROCOCCUS  OF  PNEUMONIA 206 

10. — MICROCOCCUS  OF  PUS-FORMATION     ....  266 

ii. — MICROCOCCUS  OF  ERYSIPELAS,  ETC 267 

12. — BACILLUS  OF  TETANUS 273 


PART  FIRST 

INFECTION,  DISINFECTION,  AND  IMMUNITY 


CHAPTER  I 

GENERAL  REMARKS  UPON  INFECTION 

J\  A  UCH  confusion  exists  in  the  popular  use  of  the 
*  "  term  "  infection."  By  many  it  is  supposed  to 
be  synonymous  with  contagion.  But  this  is  not  in  ac- 
cordance with  established  usage  among  well-informed 
physicians.  It  is  a  far  more  comprehensive  term  ; 
for,  while  all  contagious  diseases  are  infectious,  not 
all  infectious  diseases  are  contagious.  A  contagious 
disease  is  one  which  may  be  transmitted  by  personal 
contact,  as,  for  example,  smallpox,  measles,  scarlet 
fever.  These  diseases  may  also  be  communicated, 
indirectly,  through  the  medium  of  objects  which  have 
been  in  contact  with  infected  individuals,  such  as 
clothing,  bedding,  etc.  ("  fomites  ").  While  the  con- 
tagious diseases  mentioned  and  others  which  are  gen- 
erally recognised  as  liable  to  be  contracted  by  contact 
with  the  sick  are  also  infectious,  there  are  numerous 
diseases  which  are  infectious  but  not  contagious.  As 
examples  of  this  class  we  may  mention  the  malarial 

3 


4  INFECTION  AND  IMMUNITY 

fevers,  yellow  fever,  and  trichinosis.  Still  others, 
such  as  cholera,  typhoid  fever,  and  dysentery  are  only 
transmitted  by  personal  contact  under  very  excep- 
tional circumstances. 

The  word  "  infection,"  from  the  Latin  verb  inficio, 
means  literally  to  put  or  dip  into  anything ;  but  in  its 
accepted  technical  sense  the  putting  of  non-living 
particles  into  a  living  body  does  not  constitute  in- 
fection. A  man  who  receives  a  load  of  bird-shot  in 
the  muscles  of  his  thigh  is  not  infected  with  bird-shot 
or  with  lead.  But  when  a  living  micro-organism  is 
introduced  into  the  body  of  a  living  animal  and  multi- 
plies there,  the  animal  is  infected.  This  infection 
may  be  localised,  as  in  the  case  of  a  carbuncle,  an 
abscess,  a  pneumonia,  a  pleurisy,  etc.,  or  it  may  be 
a  general  blood  infection,  as  in  relapsing  fever,  yellow 
fever,  or  the  malarial  fevers.  In  cholera  and  dysen- 
tery the  infectious  agent  is  in  the  alimentary  canal,  and 
penetrates  to  a  greater  or  less  extent  the  mucous 
membrane  of  the  intestine.  In  typhoid  fever  it  in- 
vades the  glands  of  the  intestine  and  mesentery,  and 
the  spleen.  In  diphtheria  the  mucous  membrane  of 
the  throat  and  posterior  nares  is  the  usual  seat  of  the 
infection. 

Certain  infectious  diseases  have  their  seat  in  vari- 
ous favourite  localities  upon  the  external  portion  of 
the  body.  These  are  the  infectious  skin  diseases, 


GENERAL  REMARKS  UPON  INFECTION         5 

which  are  also  contagious  for  evident  reasons.  The 
fact  that  the  infecting  parasite  must  penetrate  the 
body  of  its  living  host  is  well  illustrated  by  the  in- 
fectious skin  disease  known  popularly  as  "  itch " 
(scabies).  The  itch  insect  deposits  its  ova  and  rears 
its  family  in  burrows  beneath  the  epidermis,  and  thus 
becomes  the  agent  in  the  production  of  an  infectious 
skin  disease.  Certain  other  parasites,  known  as 
pediculi,  infest  the  surface  of  the  body,  especially  in 
localities  covered  with  hair.  As  these  do  not  pene- 
trate the  skin,  their  presence  does  not  constitute  an 
infection. 

The  fact  that  a  disease  may  be  transmitted  through 
a  series  of  individuals  either  by  contagion  or  in  some 
other  way — by  inoculation,  by  contaminated  drink- 
ing-water, etc. — is  evidence  that  it  is  due  to  a  living 
disease  germ  of  some  kind  and  that  it  is  consequently 
infectious.  An  individual  who  has  been  stung  by 
a  wasp  or  bitten  by  a  rattlesnake  is  not  infected  but 
poisoned.  The  symptoms  resulting  from  such  a  bite 
cannot  be  reproduced  in  another  individual  by  inocu- 
lation of  blood  or  other  material  from  the  body  of 
the  person  bitten.  But  the  bite  of  a  rabid  dog  gives 
rise  to  an  infectious  disease — "  hydrophobia  "-—which 
may  be  transmitted  by  inoculation  through  a  series  of 
men  or  dogs  or  other  susceptible  animals. 

The  poison  introduced  by  a  wasp  or  rattlesnake 


6  INFECTION  AND  IMMUNITY 

does  not  multiply  in  the  body  of  the  individual  bitten 
and  the  symptoms  produced  bear  a  direct  relation  to 
the  amount  injected.  Moreover,  the  symptoms  fol- 
low very  closely  after  the  bite.  On  the  other  hand,  an 
infectious  disease  resulting  from  inoculation,  or  con- 
tracted in  any  other  way,  is  not  developed  at  once  ; 
but  after  the  introduction  of  the  infectious  material  a 
certain  interval  elapses,  technically  known  as  the 
"period  of  incubation,"  before  the  symptoms  char- 
acteristic of  the  disease  are  manifested.  In  the  case  of 
hydrophobia,  resulting  from  the  bite  of  a  rabid  animal, 
this  so-called  period  of  incubation  may  be  greatly 
prolonged.  It  is  seldom  less  than  two  weeks  and  may 
be  six  months  or  more.  But,  as  a  rule,  the  period  of 
incubation  is  quite  definite  for  each  infectious  dis- 
ease, although  differing  greatly  in  different  diseases. 
Thus  it  is  usually  less  than  three  days  in  scarlet  fever 
and  diphtheria ;  from  two  to  five  days  in  yellow  fever 
and  influenza ;  from  seven  to  ten  days  in  whooping- 
cough  ;  eleven  or  twelve  days  in  smallpox ;  fourteen 
days  in  measles ;  and  from  seventeen  to  twenty-one 
days  in  mumps.  In  wound  infections,  resulting  from 
the  introduction  of  certain  well-known  disease  germs 
into  wounds  produced  by  the  surgeon's  knife  or  other- 
wise, the  period  of  incubation  is  comparatively  short, 
and  erysipelas  or  "  blood-poisoning  "  may  be  developed 
within  a  few  hours  after  the  inoculation  occurs. 


GENERAL  REMARKS  UPON  INFECTION        7 

What  has  already  been  said  will,  it  is  hoped,  make 
the  following  definition  of  an  infectious  disease  quite 
clear.  An  infectious  disease  is  one  which  is  caused 
by  the  introduction  of  living  disease  germs  within  the 
body  of  a  susceptible  individual.  This  definition  in- 
cludes the  idea  of  the  reproduction — that  is,  multipli- 
cation within  the  body — of  the  specific  disease  germ, 
which  must  be  living  and  thus  capable  of  reproduc- 
tion in  order  to  produce  an  infectious  disease.  More- 
over, it  must  find  conditions  favourable  for  its 
reproduction  within  the  body  or  it  will  not  give  rise 
to  any  disease  process — that  is,  the  individual  must 
be  susceptible. 


CHAPTER  II 

DISEASE  GERMS 

TTAVING  ascertained  that  infection  results  from 
*  *  the  introduction  of  living  "  disease  germs  "  into 
susceptible  individuals,  it  will  be  well  to  give  some 
consideration  to  these  agents  of  infection.  The  term 
disease  germ  is  a  popular  one  and  is  used  to  desig- 
nate any  micro-organism  capable  of  giving  rise  to  an 
infectious  disease.  The  word  micro-organism,  which 
I  shall  have  frequent  occasion  to  use,  may  require  a 
little  explanation.  By  an  organism  we  mean  an  or- 
ganic structure  which  has  been  built  up  by  vital  pro- 
cesses. It  may  be  a  plant  or  an  animal,  it  may  be 
complex  or  simple,  large  or  small,  but  it  must,  at  one 
time  at  least,  have  been  endowed  with  life.  A  micro- 
organism is  simply  a  microscopic  organism,  and  being 
microscopic  it  is  an  organism  of  very  simple  structure, 
usually  consisting  of  a  single  cell  ("  unicellular  micro- 
organism ").  When  using  the  word  micro-organism 
with  reference  to  a  disease  germ,  we  must  use  an 

8 


DISEASE  GERMS  9 

adjective  to  indicate  that  the  particular  micro-organism 
under  consideration  is  capable  of  producing  disease, 
for  there  are  numerous  micro-organisms  which  are  en- 
tirely harmless.  The  word  pathogenic  literally  means 
disease-producing ;  a  pathogenic  micro-organism  is 
therefore  a  microscopic  organism  capable  of  produc- 
ing disease.  This  sounds  a  little  more  scientific  than 
"  disease  germ,"  and  it  has  seemed  to  me  necessary  to 
spend  a  little  time  in  explaining  the  meaning  of  the 
term,  as  I  may  have  occasion  to  use  it  from  time  to 
time,  although  it  is  my  intention  to  avoid  the  use  of 
technical  terms  as  far  as  possible. 

When  we  say  that  a  certain  infectious  disease  is 
due  to  a  pathogenic  micro-organism  we  have  not 
committed  ourselves  as  to  the  characters  of  this  dis- 
ease germ.  It  may  belong  to  the  animal  or  the  vege- 
table kingdom  ;  it  may  be  round  or  oval  or  spiral  in 
form  ;  it  may  be  large  or  small,  although  microscopic. 
But  when  I  speak  of  the  micrococcus  of  pneumonia 
or  the  bacillus  of  typhoid  fever,  I  am  using  terms 
which  convey  much  more  definite  information  with 
reference  to  the  disease  germs  referred  to,  and  before 
proceeding  any  farther  it  will  be  desirable  to  make 
the  reader  acquainted  with  the  principal  characters  of 
some  of  the  best-known  pathogenic  micro-organisms. 
Some  of  these  belong  to  the  animal  and  some  to  the 
vegetable  kingdom.  Although  so  very  minute  and 


io  INFECTION  AND  IMMUNITY 

simple  in  structure,  consisting,  as  a  rule,  of  a  single 
cell,  they  may  be  differentiated  by  the  expert  without 
great  difficulty,  and  classified  as  animal  micro-organ- 
isms ("Protozoa")  or  as  vegetable  micro-organisms 
("  Protophyta ").  By  far  the  greater  number  of 
known  disease  germs  are  recognised  as  vegetable 
micro-organisms  belonging  to  the  class  known  as 
Bacteria.  This  class  includes  a  large  number  of 
harmless  species,  which  abound  especially  in  surface 
waters  and  in  the  upper  layers  of  the  soil. 

The  bacteria  are  classified  with  reference  to  their 
form.  Those  which  are  spherical  are  called  micro- 
cocci /  those  which  are  longer  in  one  diameter  than 
in  the  other — oval,  rod-shaped,  or  filamentous — are 
called  bacilli ;  those  which  are  elongated  and  spiral 
in  form,  like  a  corkscrew,  are  called  spirilla  (singu- 
lar— micrococcus,  bacillus,  spirillum).  The  germs  of 
pneumonia,  of  erysipelas,  of  boils  and  abscesses,  of 
Malta  fever,  of  cerebro-spinal  meningitis,  and  some 
others  are  micrococci,  all  having  distinct  specific  char- 
acters by  which  they  can  readily  be  recognised  by  an 
expert  bacteriologist.  The  germs  of  typhoid  fever, 
of  tuberculosis,  of  influenza,  of  diphtheria,  of  dysen- 
tery, of  bubonic  plague,  of  tetanus,  and  of  several 
infectious  diseases  of  the  lower  animals  (hog  cholera, 
swine  plague,  anthrax,  glanders)  are  bacilli.  As  in 
the  case  of  the  pathogenic  micrococci,  these  all  have 


DISEASE  GERMS  n 

specific  characters  by  which  they  can  be  differentiated 
one  from  the  other,  independently  of  the  fact  that  each 
gives  rise  to  a  specific  infectious  disease.  The  germs 
of  Asiatic  cholera  and  of  relapsing  fever  are  spirilla. 

All  bacteria  multiply  by  binary  division — that  is, 
one  cell  divides  into  two,  each  resembling  in  form 
and  dimensions  the  parent  cell,  and  each  in  its  turn 
dividing  in  the  same  way.  The  rapidity  of  multipli- 
cation by  binary  division  varies  greatly  in  different 
species,  and  depends  upon  circumstances  relating  to 
temperature,  moisture,  and  suitable  nutrient  material. 
Under  favourable  conditions  bacilli  have  been  ob- 
served to  divide  in  twenty  minutes,  and,  as  each 
daughter  cell  is  equal  in  size  to  the  mother  cell,  it  is 
evident  that  an  amount  of  nutrient  material  has  been 
assimilated  during  this  time  equal  to  the  quantity 
contained  in  the  original  cell.  As  a  result  of  this 
rapid  development,  "  colonies  "  containing  millions  of 
bacilli  may  be  developed  from  a  single  cell  in  twenty- 
four  to  forty-eight  hours.  A  simple  calculation  will 
show  what  an  immense  number  of  cells  may  be  pro- 
duced in  this  time  as  a  result  of  binary  division  oc- 
curring, for  example,  every  hour.  The  progeny  of 
a  single  cell  would  be  at  the  end  of  twenty-four  hours 
16,777,220.  During  the  process  of  multiplication 
by  binary  division,  the  bacterial  cells  often  remain 
attached  to  each  other,  and  we  may  see  them  under 


12  INFECTION  AND  IMMUNITY 

the  microscope  grouped  in  pairs,  or  in  chains,  or  in 
irregular  masses. 

Some  of  the  bacteria  multiply  not  only  by  binary 
division  but  also  by  the  formation  of  spores,  which 
correspond,  so  far  as  the  preservation  of  the  species 
is  concerned,  to  the  seeds  of  higher  plants.  The 
growing  cells  are  delicate  plants  which  are  easily 
killed  by  heat  and  by  various  chemical  agents  (dis- 
infectants). But  the  spores  resist  a  much  stronger 
solution  of  germicidal  agents  and  a  much  higher 
temperature.  They  also  resist  desiccation,  and  may 
retain  their  vitality  for  months  or  years  until  circum- 
stances are  favourable  for  their  development,  when, 
under  the  influence  of  heat  and  moisture,  they  repro- 
duce the  minute  microscopic  plant — bacillus  or  spiril- 
lum— and  multiplication  by  binary  division  again 
occurs.  It  is  fortunate  that  comparatively  few  patho- 
genic bacteria  produce  spores,  for  if  this  were  the 
case  it  would  be  a  much  more  difficult  task  to  arrest 
the  progress  of  an  epidemic  of  such  diseases  as 
typhoid  fever,  bubonic  plague,  cholera,  or  diphtheria. 
The  only  infectious  disease  of  man  in  which  spores 
have  been  demonstrated  to  be  formed  is  tetanus,  or 
lockjaw.  As  this  disease  is  not  likely  to  be  com- 
municated by  the  sick  to  those  associated  with  them, 
either  directly  or  indirectly,  the  formation  of  spores 
by  the  tetanus  bacillus  is  not  so  serious  a  matter. 


DISEASE  GERMS  13 

As  to  the  structure  of  the  bacterial  cells  but  little 
can  be  said,  except  that  these  simple,  unicellular  plants 
consist  of  a  transparent  protoplasm  enclosed  in  a  cel- 
lular envelope  or  membrane.  The  very  varied  char- 
acters which  distinguish  different  species  of  bacteria 
make  it  evident  that  there  are  essential  differences 
in  the  living  cell  contents,  or  protoplasm,  although 
these  differences  are  not  revealed  by  chemical  analy- 
sis or  by  our  optical  appliances. 


CHAPTER  III 

CHANNELS  OF  INFECTION 

l^vISEASE  germs  gain  access  to  the  bodies  of  sus- 
•— ^  ceptible  individuals,  giving  rise  to  infectious 
diseases,  through  various  channels.  The  most  im- 
portant of  these  are  doubtless  the  alimentary  and 
respiratory  tracts,  to  which  access  is  obtained  through 
the  mouth  and  nasal  passages.  It  is  sometimes  diffi- 
cult to  ascertain  whether  infection  has  occurred  as  a 
result  of  the  deposition  of  germs  contained  in  inspired 
air  upon  the  mucous  membrane  of  the  respiratory 
passages  or  by  reason  of  their  having  been  taken  into 
the  stomach  with  food  or  drink. 

Germs  suspended  in  the  air  would  be  to  a  consid- 
erable extent  deposited  upon  the  moist  mucous  mem- 
brane of  the  mouth  and  nasal  passages,  and  would  be 
carried  thence  to  the  stomach  rather  than  to  the 
lungs.  However,  in  certain  diseases,  infection  no  doubt 
results  from  the  deposition  of  germs  in  the  bronchial 
tubes.  This  is  true  of  pulmonary  consumption,  of 

u 


CHANNELS  OF  INFECTION  15 

influenza  (la  grippe),  of  the  pulmonic  form  of  bubonic 
plague,  of  "  wool-sorter's  disease "  (pulmonary  an- 
thrax), and  of  pneumonia.  In  diphtheria  the  initial 
infection  commonly  occurs  upon  the  surface  of  the 
tonsils.  This  is  also,  no  doubt,  true  in  the  various 
forms  of  tonsillitis  and  possibly  in  scarlet  fever.  In- 
deed there  is  good  reason  to  believe  that  the  ton- 
sils constitute  the  avenue  through  which  infection 
occurs,  occasionally  at  least,  in  a  considerable  number 
of  diseases  of  this  class,  including  tuberculosis.  The 
exact  knowledge  which  has  been  gained  during  the 
past  twenty  years  has  made  it  evident  that  infection 
through  the  medium  of  the  air  is  by  no  means  as 
common  as  was  formerly  believed.  We  now  know 
that  malarial  fevers  and  yellow  fever  are  not  con- 
tracted in  this  way,  but  that  they  result  from  inocula- 
tions made  by  infected  mosquitoes.  Some  disease 
germs  are  quickly  killed  by  desiccation  and  exposure  to 
sunlight.  These  are  not  likely  to  be  carried  through 
the  air  in  a  living  condition,  and  consequently  the 
diseases  produced  by  them  are  not  propagated  in  this 
way.  This  is  true  of  Asiatic  cholera  and  to  a  con- 
siderable extent  of  typhoid  fever,  which  diseases  are 
recognised  as  being  essentially  water-born.  How- 
ever, the  bacillus  of  typhoid  fever  resists  desiccation 
for  some  time,  and  when  the  surface  of  the  ground 
becomes  contaminated  with  the  discharges  of  typhoid- 


1 6  INFECTION  AND  IMMUNITY 

fever  patients  the  bacillus  may  be  carried  by  the  wind, 
with  dust,  and  deposited  upon  the  moist  mucous 
membrane  of  the  mouths  and  nasal  passages  of  indi- 
viduals who  breathe  this  dust-laden  air.  This  is  also 
true  of  the  bacillus  of  bubonic  plague,  and  to  a  still 
greater  degree  of  the  bacillus  of  tuberculosis. 

The  bubonic-plague  bacillus,  contained  in  the  ex- 
creta of  infected  individuals  and  of  rats,  which  are 
very  susceptible  to  the  disease,  may  retain  its  vitality 
for  a  considerable  time  when  deposited  upon  the 
ground,  and  it  is  in  this  way  that  insanitary  localities 
become  centres  of  infection.  The  tubercle  bacillus, 
which  is  contained  in  the  matter  coughed  up  from 
the  lungs  by  persons  suffering  from  pulmonary  con- 
sumption, may  retain  its  vitality  and  infecting  power 
for  a  long  time  after  the  expectorated  material  con- 
taining it  has  been  dried  and  pulverised. 

It  is  evident  that  such  dust  is  likely  to  be  carried 
by  currents  of  air  and  deposited  in  the  lungs  of  per- 
sons who  are  compelled  to  live  in  localities  where 
such  insanitary  conditions  prevail.  No  doubt  this  is 
the  usual  way  in  which  pulmonary  consumption  is 
contracted.  Again,  the  dust  deposited  in  the  mouth 
and  nasal  passages  may  be  swallowed  and  other  forms 
of  tubercular  disease  result  —  tubercular  peritonitis, 
tubercular  meningitis,  tubercular  joint  disease,  tuber- 
culosis of  the  vertebral  column. 


CHANNELS  OF  INFECTION  17 

In  smallpox,  scarlet  fever,  and  the  "  eruptive  fevers" 
generally  infectious  material  is  given  off  from  the  sur- 
face of  the  body  of  the  sick  person.  This  is  associ- 
ated with  cast-off  epithelium,  pus  cells,  etc.,  and 
constitutes  a  kind  of  dust  which  abounds  in  the  sick- 
room and  clings  to  the  clothing  and  bedding  of  the 
patient  and  of  those  in  attendance  upon  him.  In 
influenza  and  whooping-cough  the  patient  forcibly 
ejects  small  masses  of  mucus  which  soon  become 
desiccated  and  are  likely  to  make  up  a  portion  of  the 
dust  in  apartments  occupied  by  such  patients.  Evi- 
dently the  great  danger  from  infection  in  these  dis- 
eases results  from  visiting  the  sick-room  or  handling 
clothing  which  has  been  exposed  to  contamination  by 
infectious  material  coming  from  the  body  of  the  sick 
person. 

In  typhoid  fever,  Asiatic  cholera,  and  dysentery 
the  infectious  material  coming  from  the  sick  person 
is  contained  in  the  discharges  from  the  bowels  and 
is  usually  quickly  removed  from  the  sick-room.  The 
great  danger  as  regards  the  spread  of  these  dis- 
eases consists  in  the  possibility  that  ignorant  or  care- 
less persons  may  throw  these  discharges  upon  the 
ground  or  dispose  of  them  in  some  way  which  makes 
it  possible  for  the  germs  to  be  washed  into  a  well  or 
a  running  stream  from  which  water  is  used  for  drink- 
ing purposes.  But  this  is  not  the  only  way  in  which 


1 8  INFECTION  AND  IMMUNITY 

disease  germs  may  find  their  way  from  the  excreta 
of  the  sick  to  the  stomachs  of  healthy  persons.  If 
thrown  upon  the  ground,  flies  alighting  upon  the  foul 
material  may  subsequently  visit  a  near-by  kitchen 
and  there  walk  over  the  food  prepared  for  the  family 
meal,  leaving  numerous  typhoid  bacilli  in  their  tracks  ; 
or  they  may  fall  into  the  milk,  or  in  some  other  un- 
suspected way  convey  the  deadly  microscopic  germs 
to  some  article  of  food  or  drink.  Again,  articles  of 
clothing  soiled  by  the  discharges  of  the  sick  may  be 
the  means  of  conveying  infection  to  laundresses,  who 
in  handling  such  articles  are  liable  to  soil  their  hands 
or  in  some  indirect  way  to  introduce  the  pathogenic 
bacteria  into  their  mouths.  This  mode  of  infection 
is  liable  to  occur  in  any  disease  in  which  the  germ  is 
present  in  the  discharges  from  the  bowels,  and  es- 
pecially in  Asiatic  cholera. 

In  Oriental  countries,  where  human  excreta  con- 
stitutes a  very  common  fertilising  material,  green 
vegetables,  which  are  eaten  raw,  are  believed  to 
serve  as  the  medium  through  which  the  germs  of 
dysentery  and  cholera  are  occasionally  conveyed 
to  the  stomachs  of  persons  partaking  of  such  articles 
of  food.  There  is  also  considerable  evidence  in 
favour  of  the  view  that  typhoid  fever  may  be  con- 
tracted by  eating  oysters  which  have  been  grown  in 
sewage-polluted  waters.  The  infectious  disease  known 


CHANNELS  OF  INFECTION  19 

as  trichinosis  is  contracted  by  eating  pork  containing 
living  trichinae.  As  these  parasitic  worms  are  promptly 
killed  at  a  comparatively  low  temperature,  cooked 
pork  is  quite  harmless,  so  far  as  this  disease  is  con- 
cerned. 

Infection  through  wounds  is  far  less  common  at 
the  present  day  than  was  the  case  before  aseptic  sur- 
gery and  the  antiseptic  treatment  of  wounds  became 
established  as  a  standard  method  of  surgical  proced- 
ure. Formerly  epidemics  of  septicaemia,  erysipelas, 
and  hospital  gangrene  were  of  frequent  occurrence, 
and  the  cleanest  and  best  regulated  hospitals  were 
not  exempt  from  these  visitations.  But  in  the  light 
of  our  present  knowledge  such  epidemics  are  no 
longer  excusable  and  the  infection  of  surgical  wounds 
is  extremely  rare.  Accidental  wounds  may,  however, 
become  infected  at  the  time  they  are  inflicted  or  be- 
cause of  failure  to  apply  proper  surgical  dressings. 
Jagged  and  penetrating  wounds  which  do  not  bleed 
are  especially  liable  to  be  infected  by  the  lodgment 
of  germs  in  the  deeper  portion  of  the  wound.  It  is 
in  this  way  that  tetanus  or  lockjaw  is  commonly  pro- 
duced. The  tetanus  bacillus  forms  spores  which  may 
retain  their  vitality  for  years.  These  are  found  in 
soil  which  has  been  enriched  by  manuring  and  in  the 
dust  of  streets. 

Bubonic  plague  is  another  disease  which  is  com- 


20  INFECTION  AND  IMMUNITY 

monly  contracted  through  accidental  wounds.  In 
countries  where  it  prevails,  it  has  been  observed  that 
the  natives,  who  do  not  wear  shoes  and  stockings,  are 
much  more  liable  to  infection  than  Europeans,  and  it 
seems  to  be  well  established  that  infection  may  occur 
through  insignificant  wounds,  such  as  scratches  or 
abrasions  of  exposed  parts  of  the  body.  We  have 
also  satisfactory  evidence  that  tuberculosis  may  be 
transmitted  to  man  by  the  accidental  inoculation  of 
an  open  wound.  Malignant  pustule,  or  anthrax,  is 
communicated  in  the  same  way,  and  it  sometimes 
happens  that  the  inoculation  is  effected  by  flies  which 
have  been  in  contact  with  the  infectious  material 
escaping  from  the  body  of  an  animal  having  the  dis- 
ease or  recently  dead  as  a  result  of  it. 

It  is  well  known  that  surgeons  when  operating  upon 
an  infected  wound  and  pathologists  when  performing 
autopsies,  in  certain  cases,  are  liable  to  a  severe  and 
sometimes  fatal  attack  of  "blood-poisoning"  as  a 
result  of  infection  through  a  slight  scratch  or  abra- 
sion upon  the  hand,  or  through  an  accidental  punc- 
ture made  by  a  surgical  needle.  The  germ  which  is 
most  frequently  concerned  in  this  blood-poisoning,  or 
septicaemia,  is  well  known  and  is  the  usual  cause  of 
puerperal  fever,  erysipelas,  and  a  considerable  propor- 
tion of  the  cases  of  peritonitis.  It  is,  therefore,  in 
treating  or  making  autopsies  upon  cases  of  this  nature 


CHANNELS  OF  INFECTION  2 1 

that  physicians  run  the  greatest  danger  of  accidental 
infection. 

The  question  whether  infection  may  occur  through 
the  unbroken  skin  has  been  studied  and  an  affirma- 
tive result  obtained.  The  liability  to  infection  in  this 
way  is,  however,  comparatively  slight.  When  it  does 
occur,  it  appears  that  the  germs  penetrate  through 
the  hair  follicles.  Infection  may  occur  through  mu- 
coiis  membranes,  and  it  is  in  this  way  that  infectious 
conjunctivitis  and  various  other  specific  inflamma- 
tions of  mucous  membranes  are  propagated.  Infec- 
tious skin  diseases,  such  as  scabies  (itch),  ringworm, 
barber's  itch,  etc.,  may,  no  doubt,  be  contracted  by 
susceptible  persons,  when  conditions  are  favourable, 
independently  of  any  wound  or  abrasion,  especially 
in  those  who  do  not  indulge  in  frequent  bathing  and 
thus  give  the  germs  time  to  penetrate  the  epidermis. 

Researches  made  during  the  past  few  years  have 
demonstrated  that  malarial  fevers  and  yellow  fever 
are  communicated  to  man  through  the  bites  of  in- 
fected mosquitoes.  Certain  infectious  diseases  of  lower 
animals  are  also  transmitted  by  insects.  Thus  it  has 
been  shown  that  ticks  are  responsible  for  the  propa- 
gation of  a  fatal  disease  of  cattle  known  as  Texas 
fever,  and  an  infectious  disease  of  horses,  which  has 
recently  prevailed  extensively  in  the  Philippine 
Islands,  is  communicated  by  a  biting  fly,  which 


22  INFECTION  AND  IMMUNITY 

transmits  the  parasite  from  diseased  to  healthy  animals 
— "  surra  disease."  The  tsetse-fly  disease  of  Africa  is 
transmitted  in  the  same  way  and  is  very  fatal  to 
horses  and  also  to  the  ox,  the  dog,  the  ass,  and  the 
sheep,  but  not  to  wild  animals  indigenous  in  the 
region  where  the  tsetse  fly  is  found.  The  parasite  is 
present  in  great  numbers  in  the  blood  of  infected 
animals,  and  the  fly  simply  acts  as  a  carrier  of  this 
parasite  from  diseased  to  healthy  animals. 


CHAPTER  IV 

SUSCEPTIBILITY  TO  INFECTION 

TT  has  long  been  known  that  certain  infectious  dis- 
eases  prevail  only  or  principally  among  animals 
of  a  single  species,  while  others  are  communicable  to 
several  species,  including  man  himself.  Thus  typhoid 
fever,  cholera,  and  relapsing  fever  are  diseases  of 
man,  and  during  their  epidemic  prevalence  none  of 
the  domestic  animals  contracts  any 'of  these  diseases. 
On  the  other  hand,  the  lower  animals  are  subject 
to  various  infectious  diseases  which  may  prevail  as 
fatal  epidemics  but  which  are  never  communicated 
to  man — for  example,  chicken  cholera,  hog  cholera, 
swine  plague,  rinderpest,  foot-and-mouth  disease. 
Again,  several  species,  including  man,  may  be  sus- 
ceptible to  a  disease  while  other  animals  have  a 
natural  immunity  to  it.  Thus  tuberculosis  is  com- 
mon to  man,  to  cattle,  to  apes,  and  to  the  small 
herbivorous  animals  (by  inoculation),  while  the  carni- 
vora,  as  a  rule,  are  immune ;  anthrax  may  be 

23 


24  INFECTION  AND  IMMUNITY 

communicated  by  inoculation  to  man,  to  cattle,  to 
sheep,  to  guinea-pigs,  rabbits,  and  mice,  but  the  rat, 
the  dog,  carnivorous  animals  generally,  and  birds  are 
immune ;  glanders,  which  is  essentially  a  disease  of 
horses,  may  be  communicated  to  man,  to  the  guinea- 
pig,  and  to  field-mice,  while  house-mice,  rabbits,  cattle, 
and  swine  are  to  a  great  extent  immune  ;  smallpox 
is  essentially  a  disease  of  man,  but  a  modified  form 
of  the  disease  may  prevail  among  cattle  (cowpox). 
Susceptibility  to  infection  also  depends  to  a  con- 
siderable extent  upon  conditions  relating  to  the  indi- 
vidual. It  is  well  known  that  an  attack  of  certain 
infectious  diseases  protects  the  individual  from  subse- 
quent attacks.  This  subject  will  receive  attention  in 
the  chapter  devoted  to  "  Acquired  Immunity."  But 
in  the  absence  of  any  such  acquired  immunity  the 
susceptibility  of  individuals  of  the  same  species  dif- 
fers considerably,  and  the  same  individual  may  be 
more  susceptible  to  infection  at  one  time  than  at 
another.  Certain  families  or  races  are  especially  sus- 
ceptible to  infection  by  certain  disease  germs.  Thus 
the  negro  race  is  less  susceptible  to  yellow  fever  and 
to  the  malarial  fevers  than  the  white  race ;  on  the 
other  hand,  smallpox  is  exceptionally  fatal  among 
negroes  and  dark-skinned  races.  In  general  it  may 
be  said  that  when  an  infectious  disease  is  first  intro- 
duced among  primitive  races,  who,  by  reason  of  their 


SUSCEPTIBILITY  TO  INFECTION  25 

isolation,  have  been  previously  exempt  from  it,  it  is 
apt  to  be  exceptionally  fatal.  This  is  no  doubt  due 
to  the  fact  that  there  has  been  no  opportunity  for  the 
operation  of  the  laws  of  natural  selection,  by  "  sur- 
vival of  the  fittest."  But  under  the  operation  of 
these  laws,  in  process  of  time,  a  certain  degree  of 
race  immunity  is  likely  to  be  established. 

Individual  susceptibility  depends  to  some  extent 
upon  age.  As  a  rule,  young  animals  are  more  sus- 
ceptible to  infection  by  inoculation  than  adults  of 
the  same  species.  In  the  human  race  we  recognise 
certain  diseases  as  especially  liable  to  prevail  among 
children — scarlet  fever,  whooping-cough,  etc.  It  is 
also  known  that  the  tendency  to  tubercular  infection 
diminishes  with  advancing  years.  Tubercular  menin- 
gitis and  tubercular  joint  diseases  are  most  common 
in  children,  and  pulmonary  consumption  in  young 
adults.  Again,  the  susceptibility  of  individuals  de- 
pends to  a  considerable  extent  upon  conditions  re- 
lating to  their  general  ,health.  Various  depressing 
agencies  increase  the  susceptibility  to  infection.  Most 
prominent  among  these  are  insufficient  food,  insani- 
tary surroundings,  great  fatigue,  and  mental  worry — 
grief,  fear,  etc.  The  fact  that  pestilence  and  famine 
are  likely  to  go  hand  in  hand  has  long  been  known. 
Whether  the  prevailing  epidemic  be  cholera,  bubonic 
plague,  relapsing  fever,  typhus,  or  smallpox,  the 


26  INFECTION  AND  IMMUNITY 

influence  of  insufficient  food  is  most  marked,  and  in 
times  of  distress,  due  to  failure  of  the  food  supply,  any 
infectious  disease  is  liable  to  exhibit  a  malignancy 
and  fatal  character,  although  under  ordinary  conditions 
it  may  be  comparatively  harmless.  Insanitary  sur- 
roundings, by  vitiating  the  air,  insufficient  ventilation 
and  overcrowding  of  dwellings,  factories,  school- 
houses,  etc. — all  have  a  tendency  to  lower  the  vital 
resisting  power  of  individuals  subjected  to  such  in- 
fluences and  to  increase  the  susceptibility  to  infec- 
tion. Debility  resulting  from  loss  of  blood  or  the 
exhaustion  following  great  fatigue  also  increases  the 
susceptibility  to  various  infectious  diseases.  Clinical 
observation  shows  that  a  similar  result  follows  the  ex- 
cessive use  of  alcoholic  drinks. 

Localised  infectious  processes  are  not  only  more 
liable  to  be  established  in  individuals  whose  vital 
energy  is  reduced  by  any  of  the  causes  mentioned, 
but  also  as  a  result  of  causes  which  reduce  the  resist- 
ing power  of  the  tissues  at  the  point  of  invasion. 
Thus  a  carbuncle  or  an  abscess  may  develop  in  tis- 
sues that  have  been  bruised  or  injured  in  any  way ; 
and  the  congestion  or  inflammation  of  the  fauces 
which  is  so  common  as  a  chronic  or  acute  condition 
—a  "sore  throat"-— no  doubt  increases  the  suscepti- 
bility to  diphtheritic  infection  in  this  locality.  It  is 
well  known  that  pneumonia  often  follows  attacks  of 


SUSCEPTIBILITY  TO  INFECTION  27 

measles,  of  influenza,  or  of  bronchitis,  in  which  dis- 
eases there  is  a  catarrhal  inflammation  of  the  bron- 
chial tubes  which  appears  to  favour  infection  by  the 
specific  micrococcus  which  is  the  usual  cause  of  pneu- 
monia. The  victims  of  chronic  alcoholism  are  es- 
pecially subject  to  pneumonia. 

Certain  occupations  increase  the  susceptibility  to 
certain  infectious  diseases.  Thus  pulmonary  con- 
sumption is  more  likely  to  be  developed  in  those  who 
lead  an  indoor  life,  whose  occupation  has  a  tendency 
to  prevent  full  expansion  of  the  lungs — tailors,  seam- 
stresses ;  and  in  persons  who  are  compelled  to  breathe 
a  dust-laden  atmosphere — factory  hands,  grinders, 
etc.  Susceptibility  to  pneumonia,  influenza,  tonsil- 
litis, and  diseases  of  the  air  passages  generally  is 
increased  by  living  in  over-heated  apartments.  Ex- 
posure to  cold,  per  se,  is  not  likely  to  increase  the 
susceptibility  to  such  infections  in  individuals  who 
are  habituated  to  living  in  the  open  air,  such  as  sail- 
ors, hunters,  soldiers  living  in  tents,  etc. 


CHAPTER  V 

DISINFECTION 

'"THE  object  of  disinfection  is  to  prevent  the  exten- 
sion of  infectious  diseases  by  destroying  the 
specific  infectious  agent  (germ)  which  gives  rise  to 
them.  This  is  accomplished  by  the  use  of  disin- 
fectants. 

The  writer,  as  chairman  of  the  Committee  on  Dis- 
infectants of  the  American  Public  Health  Associa- 
tion, in  1885,  defined  a  disinfectant  as  "an  agent 
capable  of  destroying  the  infecting  power  of  infec- 
tious material." 

In  the  preliminary  report  of  this  Committee  the 
following  general  statements  with  reference  to  disin- 
fection and  disinfectants  are  also  made  : 

"There  can  be  no  partial  disinfection  of  such  material  [that 
is,  material  containing  disease  germs]  ;  either  its  infecting  power 
is  destroyed  or  it  is  not.  In  the  latter  case  there  is  a  failure  to 
disinfect.  Nor  can  there  be  any  disinfection  in  the  absence  of 
infectious  material. 

"  Popularly,  the  term  disinfection  is  used  in  a  much  broader 

28 


DISINFECTION  29 

sense.  Any  chemical  agent  which  destroys  or  masks  bad  odours, 
or  which  arrests  putrefactive  decomposition,  is  spoken  of  as  a 
disinfectant.  And  in  the  absence  of  any  infectious  disease  it  is 
common  to  speak  of  disinfecting  a  foul  cesspool,  or  a  bad-smell- 
ing stable,  or  a  privy  vault. 

"  This  popular  use  of  the  term  had  led  to  much  misapprehen. 
sion,  and  the  agents  which  have  been  found  to  destroy  bad 
odours — deodorisers, — or  to  arrest  putrefactive  decomposition — 
antiseptics, — have  been  confidently  recommended  and  extensively 
used  for  the  destruction  of  disease  germs  in  the  excreta  of  patients 
with  cholera,  typhoid  fever,  etc. 

"  The  injurious  consequences  which  are  likely  to  result  from 
such  misapprehension  and  misuse  of  the  word  disinfectant  will  be 
appreciated  when  it  is  known  that  recent  researches  have  demon- 
strated that  many  of  the  agents  which  have  been  found  useful  as 
deodorisers,  or  as  antiseptics,  are  entirely  without  value  for  the 
destruction  of  disease  germs. 

"  This  is  true,  for  example,  as  regards  the  sulphate  of  iron,  or 
copperas,  a  salt  which  has  been  extensively  used  with  the  idea 
that  it  is  a  valuable  disinfectant.  As  a  matter  of  fact,  sulphate  of 
iron  in  saturated  solution  does  not  destroy  the  vitality  of  disease 
germs,  or  the  infecting  power  of  material  containing  them.  This 
salt  is,  nevertheless,  a  very  valuable  antiseptic,  and  its  low  price 
makes  it  one  of  the  most  available  agents  for  the  arrest  of  putre- 
factive decomposition. 

"  Antiseptic  agents  also  exercise  a  restraining  influence  upon 
the  development  of  disease  germs,  and  their  use  during  epidemics 
is  to  be  recommended  when  masses  of  organic  material  in  the 
vicinity  of  human  habitations  cannot  be  completely  destroyed,  or 
removed,  or  disinfected. 

"  While  an  antiseptic  agent  is  not  necessarily  a  disinfectant,  all 
disinfectants  are  antiseptics;  for  putrefactive  decomposition  is 
due  to  the  development  of  *  germs  '  of  the  same  class  as  that 
to  which  disease  germs  belong,  and  the  agents  which  destroy  the 
latter  also  destroy  the  bacteria  of  putrefaction,  when  brought  in 
contact  with  them  in  sufficient  quantity,  or  restrain  their  develop- 
ment when  present  in  smaller  amounts. 


30  INFECTION  AND  IMMUNITY 

"  A  large  number  of  the  proprietary  '  disinfectants '  so-called, 
which  are  in  the  market,  are  simply  deodorisers  or  antiseptics  of 
greater  or  less  value,  and  are  entirely  untrustworthy  for  disinfect- 
ing purposes." 


The  offensive  gases  given  off  from  decomposing 
organic  material  are  no  doubt  injurious  to  health  ; 
and  the  same  is  true,  even  to  a  greater  extent,  of  the 
more  complex  products  known  as  ptomaines,  which 
are  a  product  of  the  vital  processes  attending  the 
growth  of  the  bacteria  of  putrefaction  and  allied 
organisms.  It  is  therefore  desirable  that  these  pro- 
ducts should  be  destroyed  ;  and,  as  a  matter  of  fact, 
they  are  neutralised  by  some  of  the  agents  which  we 
recognise  as  disinfectants,  in  accordance  with  the 
strict  definition  of  the  term.  But  they  are  also  neu- 
tralised by  other  agents — deodorants — which  cannot 
be  relied  upon  for  disinfecting  purposes,  and  by  dis- 
infectants, properly  so-called,  in  amounts  inadequate 
for  the  accomplishment  of  disinfection.  Their  form- 
ation may  also  be  prevented  by  the  use  of  antiseptics. 
From  our  point  of  view,  the  destruction  of  sulphur- 
etted hydrogen,  of  ammonia,  or  even  of  the  more 
poisonous  ptomaines,  in  a  privy  vault,  is  no  more  dis- 
infection than  is  the  chemical  decomposition  of  the 
same  substances  in  a  chemist's  laboratory.  The  same 
is  true  as  regards  all  of  the  bad-smelling  and  little- 
known  products  of  decomposition.  None  of  these 


DISINFECTION   ,.  31 

is  "  infectious  material,"  in  the  sense  in  which  we 
use  these  words ;  that  is,  they  do  not,  so  far  as  we 
know,  give  rise  directly  to  any  infectious  disease. 
Indirectly  they  are  concerned  in  the  extension  of  the 
"  filth  diseases,"  such  as  cholera,  bubonic  plague,  and 
typhoid  fever.  This  because  persons  exposed  to  the 
foul  emanations  from  sewers,  privy  vaults,  and  other 
receptacles  of  filth  have  their  vital  resisting  power 
lowered  by  the  continued  respiration  of  an  atmo- 
sphere contaminated  with  these  poisonous  gases,  and 
are  liable  to  become  the  victims  of  any  infectious  dis- 
ease to  which  they  may  be  exposed. 


CHAPTER  VI 

TESTS  OF  DISINFECTION 

\  \  7  HAT  means  have  we  of  proving  that  the  infect- 
ing power  of  infectious  material  has  been  de- 
stroyed ? 

Evidence  of  disinfection  may  be  obtained  :  (a)  from 
the  practical  experiments — experience — of  those  en- 
gaged in  sanitary  work  ;  (f)  by  inoculation  experi- 
ments upon  susceptible  animals  ;  (c)  by  experiments 
made  directly  upon  known  disease  germs. 

(a)  It  is  a  matter  of  common  experience  that,  when 
a  room  has  been  occupied  by  a  patient  with  an  infec- 
tious disease,  such  as  smallpox,  scarlet  fever,  or 
diphtheria,  susceptible  persons  are  liable  to  contract 
the  disease  weeks  or  even  months  after  the  patient 
has  been  removed  from  it,  unless  in  the  meantime  it 
has  been  disinfected.  If  a  second  case  does  occur 
from  exposure  in  such  a  room,  it  is  evident  that  it  has 
not  been  disinfected.  But  the  non-occurrence  of  sub- 
sequent cases  cannot  always  be  taken  as  evidence 

32 


TESTS  OF  DISINFECTION  33 

that  the  means  of  disinfection  resorted  to  were  effi- 
cient. Negative  evidence  should  be  received  with 
great  caution.  In  the  first  place,  the  question  as  to 
whether  susceptible  individuals  have  been  fairly  ex- 
posed in  the  disinfected  room  must  be  considered. 
Then  it  must  be  remembered  that  susceptible  persons 
do  not  always  contract  a  disease,  even  when  they  are 
exposed  in  a  locality  known  to  be  infected.  A  further 
difficulty  in  estimating  the  value  of  evidence  obtained 
in  practice  arises  from  the  fact  that  in  connection 
with  the  special  means  of  disinfection  resorted  to, 
such  as  fumigation,  hanging  up  cloths  saturated  with 
a  disinfecting  solution,  etc.,  it  is  customary  to  resort 
to  additional  precautionary  measures,  such  as  wash- 
ing surfaces  with  soap  and  hot  water,  whitewashing 
plastered  walls,  and  free  ventilation.  It  is  apparent 
that  under  these  circumstances  it  would  be  unsafe  to 
accept  the  fact  that  no  other  cases  occurred  in  a  room 
treated  in  this  way  as  evidence  that  the  particular 
disinfectant  used  is  efficient  for  the  destruction  of  the 
infectious  agent  of  the  disease  in  question.  The  fond 
mother  who  attaches  a  charm  to  her  child's  neck  to 
protect  it  from  evil  also  takes  the  precaution  of  guard- 
ing it  from  contact  with  other  children  who  are  sick 
with  any  infectious  disease.  If  her  child  fortunately 
grows  to  manhood  or  womanhood  without  having 
suffered  an  attack  of  scarlet  fever  or  diphtheria,  she 


34  INFECTION  AND  IMMUNITY 

may  imagine  that  her  charm  has  protected  it ;  but 
the  evidence  upon  which  her  faith  is  founded  is  not 
of  a  nature  to  convince  those  who  are  familiar  with 
scientific  methods  of  demonstration.  "  Well  edu- 
cated "  persons  are  often  ready  to  testify  in  favour 
of  methods  of  disinfection  or  of  treatment  upon  evid- 
ence which,  from  a  scientific  point  of  view,  has  no 
more  value  than  that  which  the  fond  mother  in  ques- 
tion has  to  offer  in  favour  of  the  little  bag  containing 
camphor  or  assafcetida  or  some  other  charm  of  equal 
value  which  she  has  attached  to  her  child's  neck  to 
keep  it  from  catching  scarlet  fever  or  diphtheria  at 
school.  On  a  par  with  these  charms,  so  far  as  disin- 
fection is  concerned,  we  may  place  the  saucer  of 
chloride  of  lime,  which  it  was  formerly  the  fashion  to 
place  under  the  bed  of  a  patient  sick  with  an  infec- 
tious disease,  the  rag  saturated  with  carbolic  acid  or 
chloride  of  zinc,  suspended  in  the  sick-room,  and  even 
the  fumigations  with  burning  sulphur,  as  sometimes 
practised  by  those  who  are  unfamiliar  with  the  evid- 
ence as  to  the  exact  value  of  this  agent  and  the 
conditions  necessary  to  insure  successful  disinfection 
with  it. 

Chloride  of  lime,  sulphurous-acid  gas,  and  carbolic 
acid  are  among  our  most  useful  disinfecting  agents ; 
but  disease  germs  cannot  be  charmed  away  by  them 
any  more  than  by  a  little  bag  of  camphor. 


TESTS  OF  DISINFECTION  35 

Having  pointed  out  the  fact  that  negative  evidence, 
in  a  restricted  field  of  observation,  must  be  accepted 
with  great  caution  in  estimating  the  value  of  disin- 
fectants, we  hasten  to  say  that  the  combined  experi- 
ence of  sanitarians,  derived  from  practical  efforts  to 
restrict  the  extension  of  infectious  diseases,  is  of  the 
greatest  value,  and  that  this  experience  is,  to  a  great 
extent,  in  accord  with  the  results  of  exact  experi- 
ments made  in  the  laboratory. 

(6)  Inoculation  experiments  upon  susceptible  ani- 
mals, made  directly  with  infectious  material  which 
has  been  subjected  to  the  action  of  a  disinfectant, 
have  been  made  by  numerous  observers.  The  proof 
of  disinfection  in  this  case  is  failure  to  produce  the 
characteristic  symptoms  which  result  from  inoculation 
with  similar  material  not  disinfected.  Thus,  Davaine 
found  that  the  blood  of  an  animal  just  dead  from  the 
disease  known  by  English  writers  as  anthrax  or 
splenic  fever,  inoculated  into  a  healthy  rabbit  or 
guinea-pig,  in  the  smallest  quantity,  infallibly  pro- 
duces death  within  two  or  three  days ;  and  the  blood 
of  these  animals  will  again  infect  and  cause  the  death 
of  others,  and  so  on  indefinitely.  This  anthrax  blood 
therefore  is  infectious  material,  which  can  be  utilised 
for  experiments  relating  to  the  comparative  value  of 
disinfectants.  Davaine  made  many  such  experiments, 
not  only  with  the  blood  of  anthrax,  but  also  with  that 


36  INFECTION  AND  IMMUNITY 

of  a  fatal  form  of  septicaemia  in  rabbits,  which  is 
known  by  his  name.  Other  investigators  have  fol- 
lowed up  these  experiments  upon  infectious  material 
of  the  same  kind,  and  also  upon  material  from  other 
sources — the  infectious  material  of  glanders,  of  tuber- 
culosis, of  symptomatic  anthrax,  of  fowl  cholera,  of 
swine  plague,  etc. 

It  has  been  proved  that  the  infectious  agent  in  all 
of  the  diseases  mentioned  is  a  living  germ,  and  that 
disinfection  consists  in  destroying  the  vitality  of  this 
germ.  But  in  experiments  made  with  blood  or  other 
material  obtained  directly  from  diseased  animals,  the 
results  would  be  just  as  definite  and  satisfactory  if 
we  were  still  ignorant  as  to  the  exact  nature  of  the 
infecting  agent.  The  test  shows  the  destruction  of 
infecting  power  without  any  reference  to  the  cause 
of  the  special  virulence,  which  is  demonstrated  to  be 
neutralised  by  certain  chemical  agents  in  a  given 
amount.  All  of  the  experiments  made  with  the 
above-mentioned  kinds  of  virus  have  been  made 
upon  the  lower  animals  ;  but  there  is  one  kind  of 
material  which  it  is  justifiable  to  use  upon  man 
himself,  and  with  which  numerous  experiments  of  a 
very  satisfactory  character  have  been  made.  This 
material  is  vaccine  virus.  Fresh  vaccine,  when  inocu- 
lated into  the  arm  of  an  unvaccinated  person,  gives 
rise  to  a  very  characteristic  result  —  the  vaccine  vesi- 


TESTS  OF  DISINFECTION  37 

cle.  The  inference  seems  justified  that  any  agent 
which  will  neutralise  the  specific  infecting  power  of 
this  material  will  also  neutralise  the  smallpox  virus. 
In  these  experiments  the  more  careful  investigators 
have  taken  the  precaution  of  vaccinating  the  same 
person  with  disinfected  and  non-disinfected  virus  from 
the  same  source.  A  successful  vaccination  with  the 
non-disinfected  virus  shows  that  the  individual  is 
susceptible  and  the  material  good  ;  failure  to  produce 
any  result  is  evidence  that  the  potency  of  the  disin- 
fected virus  has  been  destroyed  by  the  chemical 
agent  to  which  it  was  exposed. 

(c)  As  already  stated,  it  has  been  demonstrated 
that  the  infectious  diseases  of  the  lower  animals, 
which  have  furnished  the  material  for  experiments 
upon  disinfectants  by  the  method  of  inoculation,  are 
"germ  diseases,"  and  that  the  infectious  agent  is  in 
each  case  a  living  micro-organism,  belonging  to  the 
class  known  under  the  general  name  of  Bacteria. 
The  bacteria  are  vegetable  organisms,  which,  by 
reason  of  their  minute  size  and  simple  organisation 
must  be  placed  at  the  very  foot  of  the  scale  of  living 
things ;  but  they  make  up  in  number  and  in  rapidity 
of  development  for  their  minute  size. 

Many  of  these  disease  germs  are  now  known  to 
us,  not  only  by  microscopic  examination  of  the  blood 
and  tissues  of  infected  animals,  but  also  by  "  culture 


38  IXFECTION  AND  IMMUNITY 

experiments."  That  is,  we  are  able  to  cultivate  them 
artificially  in  suitable  media,  and  to  study  their  mode 
of  'development  in  the  laboratory,  quite  independently 
of  the  animals  from  which  our  "  pure  cultures  "  were 
obtained  in  the  first  instance.  The  culture  fluids 
used  are  prepared  from  the  flesh  of  various  animals  ; 
and  when  to  one  of  these  a  certain  quantity  of  gela- 
tine is  added,  we  have  a  "solid  culture  medium," 
upon  the  surface  of  which  some  of  these  germs  will 
grow  most  luxuriantly.  To  start  such  a  "  culture,"  it 
is  only  necessary  to  transfer,  with  proper  precautions, 
a  minute  quantity  of  the  infectious  material  to  the 
surface  of  our  culture  medium,  or  into  a  fluid  which 
has  been  found  to  be  suitable  for  the  growth  of  the 
particular  organism  which  we  desire  to  cultivate.  A 
second  culture  is  in  the  same  way  started  from  the 
first,  and  so  on  indefinitely. 

Now  it  is  evident  that  these  pure  cultures  furnish 
us  a  ready  means  for  testing  the  power  of  various 
chemical  agents  to  destroy  the  vitality  of  known  dis- 
ease germs,  as  shown  by  their  failure  to  grow  in  a 
suitable  culture  medium  after  exposure  for  a  given 
time  to  a  given  percentage  of  the  disinfectant.  Very 
many  experiments  of  this  nature  have  been  made. 
We  may  say  here,  that  the  experimental  data  on 
record  indicate  that  those  agents  which  are  efficient 
for  the  destruction  of  any  one  of  the  pathogenic 


TESTS  OF  DISINFECTION  39 

organisms  upon  which  experiments  have  been  made, 
or  of  harmless  species  of  the  same  class,  are  efficient 
for  the  destruction  of  all,  in  the  absence  of  spores. 
There  is,  it  is  true,  within  certain  limits,  a  difference 
in  the  resisting  power  of  different  organisms  of  this 
class  to  chemical  agents.  This  is  not,  however,  suffi- 
ciently marked  to  prevent  the  general  statement  that 
a  disinfectant  for  one  is  a  disinfectant  for  all,  in  the 
absence  of  spores. 

The  last  clause  of  the  above  statement  calls  for  an 
explanation,  and  certain  details  with  reference  to  the 
mode  of  reproduction  of  disease  germs.  All  of  the 
bacteria  multiply  by  binary  division  ;  that  is,  one  in- 
dividual divides  into  two,  and  each  member  of  the 
pair  again  into  two,  and  so  on.  The  spherical  bac- 
teria, known  as  micrococci,  multiply  only  in  this  way, 
but  some  of  the  rod-shaped  bacteria,  or  bacilli,  also 
form  spores.  These  spores  correspond  with  the  seeds 
of  higher  plants.  They  are  highly  refractive,  oval  or 
spherical  bodies,  which,  under  certain  circumstances, 
make  their  appearance  in  the  interior  of  the  rods, 
which  cease  to  multiply  by  binary  division  when  spore 
formation  has  taken  place.  The  point  of  special  in- 
terest with  reference  to  these  spores  is,  that  they  have 
a  resisting  power  to  heat,  and  to  the  action  of  chem- 
ical disinfectants,  far  beyond  that  which  is  possessed 
by  micrococci,  or  by  bacilli  without  spores.  The 


40  INFECTION  AND  IMMUNITY 

difference  may  be  compared  to  the  difference  between 
a  tender  plant  and  its  seeds  to  deleterious  influences, 
such  as  extremes  of  heat  and  cold.  Thus  the  spores 
of  certain  species  of  bacilli  withstand  a  boiling  tem- 
perature for  several  hours,  while  a  temperature  of 
150°  Fahr.  quickly  kills  most  bacteria  in  the  absence 
of  spores.  A  similar  difference  is  shown  as  regards 
the  action  of  chemical  agents.  Certain  agents, — 
e.  g.,  sulphurous-acid  gas  and  carbolic  acid, — which 
are  extensively  used  as  disinfectants,  have  been 
proved  by  exact  experiments  to  be  quite  impotent  for 
the  destruction  of  spores.  This  being  the  case,  it  is 
advisable,  in  practical  disinfection,  always  to  use  an 
agent  which  has  the  power  of  destroying  spores,  in 
those  cases  in  which  the  exact  nature  of  the  disease 
germ  has  not  been  demonstrated.  The  cholera  germ 
of  Koch  does  not  form  spores  ;  and  there  is  good 
reason  to  believe  that  the  same  is  true  as  regards  the 
germs  of  yellow  fever,  of  scarlet  fever,  and  of  small- 
pox, which  have  not  yet  been  demonstrated.  This 
inference  is  based  upon  evidence  obtained  in  the  prac- 
tical use  of  disinfectants,  and  upon  certain  facts  relat- 
ing to  the  propagation  of  these  diseases. 

A  second  general  statement,  which  is  justified  by 
the  experimental  evidence  on  record,  is,  that  agents 
which  kill  bacteria  in  a  certain  amount  prevent  their 
multiplication  in  culture  fluids,  when  present  in  quan- 


TESTS  OF  DISINFECTION  41 

tities  considerably  less  than  are  required  to  completely 
destroy  vitality. 

An  agent,  therefore,  which  in  a  certain  proportion 
and  in  a  given  time  acts  as  a  "  germicide,"  in  a  smaller 
quantity  may  act  as  an  antiseptic — i.  e.,  may  prevent 
putrefactive  decomposition  by  restraining  the  devel- 
opment of  the  bacteria  of  putrefaction.  Antiseptics 
also  prevent  or  retard  the  development  of  pathogenic 
bacteria.  It  follows  from  this  that  germicides  are 
also  antiseptics  ;  but  the  reverse  of  this  proposition  is 
not  true  as  a  general  statement,  for  all  antiseptics  are 
not  germicides.  Thus  alcohol,  common  salt,  sul- 
phate of  iron,  and  many  other  substances  which  are 
extensively  used  as  antiseptics,  have  scarcely  any 
germicide  power,  even  in  concentrated  solutions, 
and  consequently  would  be  entirely  unreliable  as 
disinfectants. 

Practically,  antiseptics  may  accomplish  the  same 
result  in  the  long  run  as  we  obtain  in  a  short  time 
by  the  use  of  disinfectants.  If,  for  example,  we  pre- 
vent the  development  of  the  germs  of  cholera,  or 
of  typhoid  fever,  in  an  infected  privy  vault,  by  the 
continued  use  of  antiseptics,  these  germs  will  in  time 
lose  their  ability  to  grow,  when  introduced  into  a 
suitable  culture  medium.  But  in  the  meantime  there 
is  always  the  possibility  that  some  of  them  may 
escape,  with  the  fluid  contents  of  the  vault,  into  the 


42  INFECTION  AND  IMMUNITY 

surrounding  soil,  and  contaminate  some  well  or  stream 
from  which  drinking-water  is  obtained.  For  this 
reason  privy  vaults,  cesspools,  and  sewers  should 
never  be  allowed  to  become  infected.  All  infectious 
material,  such  as  the  dejections  of  patients  with 
cholera  or  typhoid  fever,  should  be  destroyed  at  its 
source,  in  the  sick-room  ;  or,  if  it  is  ascertained  that 
such  material  has  been  thrown  into  a  privy  vault,  the 
entire  contents  of  the  vault  should  be  promptly  disin- 
fected. The  same  rule  applies  to  infectious  material 
thrown  upon  the  ground,  or  wherever  it  may  be. 


CHAPTER  VII 

DISINFECTION  BY  HEAT 

TT  is  hardly  necessary  to  say  that  burning  of  in- 
*  fectious  material,  infected  clothing,  etc.,  is  an 
effectual  method  of  disposing  of  it.  This  method 
of  disinfection  is  always  to  be  recommended,  when 
practical  and  consistent  with  a  due  regard  for  econ- 
omy and  the  rights  of  individuals.  As  a  rule,  arti- 
cles of  little  value,  which  have  been  soiled  with 
infectious  material,  had  better  be  burned  ;  and  this 
is  especially  true  of  old  clothing  and  bedding.  But 
we  have  other  efficient  methods  of  disinfection,  which 
make  it  unnecessary  to  sacrifice  articles  of  value  ex- 
cept under  unusual  circumstances. 

While  all  disease  germs  are  readily  killed  by  ex- 
posure for  a  short  time  to  the  temperature  of  boiling 
water,  many  of  the  most  important  pathogenic  bac- 
teria are  quickly  destroyed  by  a  much  lower  tempera- 
ture than  this — that  is,  when  exposed  in  a  liquid  or  in 
a  moist  condition.  When  in  a  desiccated  condition, 

43 


44  INFECTION  AND  IMMUNITY 

or  exposed  to  the  action  of  hot,  dry  air,  a  much  higher 
temperature  is  required.  This  fact  must  constantly 
be  kept  in  view  in  carrying  out  practical  measures  of 
disinfection,  and  for  this  reason  the  disinfection  of 
clothing,  blankets,  etc.,  by  dry  heat  is  rarely  employed. 
At  quarantine  stations  and  municipal  disinfecting  sta- 
tions disinfection  by  steam  is  relied  upon  to  a  great 
extent,  and  has  been  proved  by  experience  to  be  su- 
perior to  all  other  methods.  The  disinfection  of 
bandages,  instruments,  and  dressings  of  all  kinds  for 
the  "  aseptic "  treatment  of  surgical  wounds  is  also 
accomplished  by  exposure  to  moist  heat  (steam  or 
boiling  water). 

In  considering  the  value  of  heat  as  a  disinfectant, 
we  must  take  account  of  the  very  great  difference  in 
the  resisting  power  of  growing  bacteria  and  of  the 
reproductive  elements  formed  by  some  of  them, 
which  are  known  as  "  spores." 

The  spores  of  certain  bacteria  found  in  surface 
water  and  in  the  soil  may  resist  the  temperature 
of  boiling  water  or  of  live  steam  for  several  hours, 
but  fortunately  the  spores  of  known  disease  germs 
have  far  less  resisting  power.  In  experiments  made 
nearly  twenty  years  ago,  I  found  that  the  spores  of 
the  anthrax  bacillus  did  not  grow  after  exposure  to 
the  temperature  of  boiling  water  for  four  minutes. 

As   already   stated,   bacteria  which    do    not    form 


DISINFECTION  J3  Y  HE  A  T  45 

spores  are  quickly  killed  by  a  temperature  consider- 
ably below  that  of  boiling  water.  The  exact  thermal 
death-point  of  a  considerable  number  of  the  most 
important  disease  germs  was  determined  by  the 
writer  in  a  series  of  experiments  made  in  1885.  The 
cholera  germ  and  the  micrococcus  of  pneumonia  were 
the  least  resistant  of  all  those  tested,  and  were  de- 
stroyed by  ten  minutes'  exposure  to  a  temperature  of 
130°  Fahr.  The  typhoid  bacillus  was  killed  in  the 
same  time  by  a  temperature  of  140°.  In  general  the 
statement  may  be  made  as  a  result  of  my  own  experi- 
ments and  those  of  other  investigators,  that  patho- 
genic bacteria  which  do  not  form  spores  are  killed  by 
ten  minutes'  exposure  to  a  temperature  of  140° 
Fahr.  (moist  heat),  with  the  exception  of  the  tuber- 
cle bacillus,  which  requires  a  somewhat  higher  tem- 
perature (160°  Fahr.).  The  list  of  known  disease 
germs  which  are  killed  by  ten  minutes'  exposure 
to  a  temperature  of  140°  Fahr.  (60°  C.)  includes  the 
bacillus  of  typhoid  fever,  of  diphtheria,  of  bubonic 
plague,  of  glanders,  the  micrococcus  of  pneumonia, 
of  erysipelas  and  puerperal  fever,  of  boils  and  ab- 
scesses, the  spirillum  of  cholera  and  of  relapsing  fe- 
ver. In  addition  to  these  known  germs  it  has  been 
determined  that  the  same  temperature  destroys  the 
infecting  power  of  vaccine  virus,  and  presumably  of 
smallpox  virus,  of  hydrophobia  virus,  and  of  certain 


46  INFECTION  AND  IMMUNITY 

other  kinds  of  infectious  material  in  which  the  spe- 
cific germ  has  not  yet  been  demonstrated. 

While  dry  hot  air  is,  as  a  rule,  unreliable  for  the  de- 
struction of  disease  germs,  certain  bacteria  are  quickly 
destroyed  by  desiccation.  This  is  true  of  the  cholera 
spirillum  and  of  the  micrococcus  of  pneumonia.  On 
the  other  hand,  the  bacillus  of  typhoid  fever,  the  bacil- 
lus of  diphtheria,  the  bacillus  of  tuberculosis  and  the 
bacillus  of  bubonic  plague  may  retain  their  vitality  for 
weeks,  or  even  months,  when  in  a  desiccated  condi- 
tion. This  is  true  also  of  the  virus  of  smallpox  and 
of  scarlet  fever. 

Low  temperatures  do  not  destroy  bacteria.  They 
have  been  exposed  to  a  temperature  of—  87°  C.,  ob- 
tained by  the  evaporation  of  liquid  carbonic  acid, 
but  when  again  brought  under  favourable  conditions 
showed  no  diminution  in  their  capacity  for  develop- 
ment. Repeated  freezing  and  thawing  has,  however, 
a  deleterious  action.  The  typhoid  bacillus  may  be 
killed  in  cultures  which  are  frozen  and  thawed  out  at 
intervals  of  three  days,  by  repeating  the  operation 
five  or  six  times. 

The  facts  stated  in  this  chapter  make  it  evident 
that  heat  constitutes  the  most  generally  useful  agent 
for  the  destruction  of  infectious  material.  Any  arti- 
cle of  food  or  drink  which  has  been  recently  brought 
to  a  temperature  approaching  that  of  the  boiling- 


DISINFECTION  B  Y  HE  A  T  47 

point  is  surely  free  from  living  disease  germs  dan- 
gerous to  man. 

All  articles  of  clothing  which  have  been  subjected 
to  the  ordinary  operations  of  the  laundry  are  safely- 
disinfected. 

Vessels  containing  the  infectious  discharges  of  per- 
sons suffering  from  cholera,  typhoid  fever,  etc.,  if 
thoroughly  treated  with  boiling  water  may  be  disin- 
fected, together  with  their  contents.  To  make  sure 
of  this  the  quantity  of  boiling  water  used  should  be 
three  or  four  times  greater  than  the  contents  of  the 
vessel,  and  from  ten  to  twenty  minutes  should  be 
given  for  the  disinfecting  action  of  the  hot  water. 

Articles  of  bedding  and  clothing  which  would  be 
injured  by  immersion  in  boiling  water  may  be  disin- 
fected by  exposure  to  steam  in  a  properly  constructed 
disinfecting  chamber  or  "  steriliser." 

Clothing  may  also  be  disinfected  by  dry  heat  if 
freely  exposed  in  a  closed  chamber  to  the  action  of 
hot  dry  air,  at  a  temperature  of  125°  C.  for  two 
hours. 


CHAPTER   VIII 

SUNLIGHT  AS  A   DISINFECTANT 

\  A  7 HAT  has  been  said  in  the  preceding  chapter 
with  reference  to  the  germicidal  value  of  heat 
and  desiccation  would  indicate  the  utility  of  exposing 
infected  articles  to  sunshine  in  the  open  air,  as  has 
long  been  the  custom  in  domestic  sanitary  practice. 
But  it  has  been  ascertained  by  carefully  conducted 
experiments  that  such  exposure  has  an  additional 
value  on  account  of  the  disinfecting  action  of  the 
sunlight  per  se.  As  long  ago  as  1877  two  English 
experimenters  (Downes  and  Blunt)  in  a  communica- 
tion made  to  the  Royal  Society  of  London  presented 
evidence  showing  that  sunlight  has  an  injurious  effect 
upon  bacteria,  and  that  sterilisation  of  cultures  in 
liquid  media  could  be  effected  by  prolonged  exposure 
to  direct  sunlight.  Since  then  many  experiments 
have  been  made  by  different  observers  and  the  fact 
has  been  fully  confirmed.  Even  the  spores  of  cer- 
tain bacilli  are  destroyed  by  long  exposure  to  sun- 

48 


SUNLIGHT  AS  A  DISINFECTANT  49 

light.  The  distinguished  German  bacteriologist, 
Dr.  Robert  Koch,  reported,  some  years  since,  the 
results  of  his  experiments  with  the  tubercle  bacil- 
lus. He  found  that  the  time  required  to  kill  this 
bacillus  varies  from  a  few  minutes  to  several  hours, 
depending  upon  the  thickness  of  the  layer  exposed. 
Even  diffused  daylight  exerts  a  certain  germicidal 
action,  although  the  time  of  exposure  is  very  much 
longer — five  to  seven  days  for  the  tubercle  bacillus. 
In  the  writer's  experiments  made  in  1892  it  was 
found  that  two  hours'  exposure  to  direct  sunlight 
was  fatal  to  the  cholera  spirillum  suspended  in  a 
liquid  medium. 

The  electric  light,  and  even  gas-light,  have  also 
a  germicidal  action  upon  certain  disease  germs,  al- 
though very  much  less  in  degree  than  sunlight.  It 
has  been  ascertained  that  the  rays  at  the  violet  end  of 
the  spectrum  have  the  greatest  disinfecting  power, 
while  the  red  rays  are  comparatively  inert. 

The  facts  stated  fully  sustain  the  popular  idea  that 
the  exposure  of  infected  articles  of  clothing  and  bed- 
ding in  the  sun  is  a  useful  sanitary  precaution.  Re- 
peated and  prolonged  exposure  will,  however,  be 
necessary  to  ensure  safety.  In  the  case  of  such  dis- 
eases as  smallpox,  diphtheria,  and  scarlet  fever  more 
speedy  and  reliable  measures  of  disinfection  will  be 
required.  Exposure  to  the  sunlight  is  nevertheless  a 


50  INFECTION  AND  IMMUNITY 

most  useful  and  economical  procedure  and  is  to  be 
commended  as  a  routine  practice  in  domestic  sanita- 
tion, and  also  as  an  additional  and  supplementary 
precaution  when  infected  articles  have  been  subjected 
to  the  action  of  other  disinfectants. 


CHAPTER  IX 

DISINFECTION  BY  GASES 

TT  is  impracticable  to  disinfect  the  atmosphere  of  an 
occupied  apartment ;  for  any  gaseous  or  volatile 
agent  which  would  destroy  disease  germs  suspended 
in  the  air  would  render  it  irrespirable.  Moreover  the 
air  of  the  sick-room  should  be  constantly  renewed  by 
ventilation,  and  there  is  far  less  reason  for  disinfect- 
ing it  when  the  patient  has  been  removed  than  while 
it  is  occupied,  for  then  the  air  may  be  quickly  re- 
newed by  opening  doors  and  windows.  As  is  well 
known,  particles  of  dust  suspended  in  the  air  of  a 
room  have  a  tendency  to  settle  upon  the  floor,  upon 
window  ledges,  etc.,  and  infected  particles  from  the 
patient's  body  will  constitute  a  portion  of  this  dust  in 
such  diseases  as  smallpox  and  scarlet  fever,  while  in 
tuberculosis,  diphtheria,  influenza,  and  pneumonia 
expectorated  material  may  become  desiccated  and 
constitute  a  portion  of  the  dust. 

Every  effort  should  be  made  to  prevent  a  room 

51 


52  INFECTION  AND  IMMUNITY 

occupied  by  patients  sick  with  an  infectious  disease 
from  becoming  infected.  Carpets,  stuffed  furniture, 
curtains,  and  other  articles  difficult  to  disinfect  should 
be  removed  at  the  outset.  Indeed,  nothing  should 
be  left  in  the  room  which  is  not  absolutely  required, 
and  all  furniture  and  utensils  should  be  of  such  a 
character  that  they  can  be  readily  disinfected  by 
washing  with  boiling  water  or  with  a  disinfecting  so- 
lution. Abundant  ventilation  and  scrupulous  cleanli- 
ness should  be  maintained,  and  a  disinfecting  solution 
should  always  be  at  hand  for  washing  the  floor,  or 
articles  in  use,  the  moment  they  are  soiled  by  infectious 
discharges. 

Daily  wiping  of  all  surfaces — floors,  walls,  and 
furniture — with  a  cloth  wet  with  a  disinfecting  solu- 
tion is  to  be  recommended.  For  this  purpose  a 
solution  of  chloride  of  lime  (2  per  cent),  or  of  car- 
bolic acid  (2  per  cent),  or  mercuric  chloride  (1:1000), 
may  be  used. 

By  such  precautions  the  infection  of  the  sick-room 
may  be  prevented,  especially  in  those  diseases,  such 
as  cholera  and  typhoid  fever,  in  which  the  infectious 
agent  is  not  given  off  from  the  general  surface  of  the 
body  of  the  sick  person. 

If  a  complete  disinfection  of  the  room  is  required  it 
is  indispensable  that  it  be  first  vacated.  It  will  then 
be  practicable  to  use  certain  gaseous  disinfectants. 


DISINFECTION  BY  GASES  53 

The  various  so-called  disinfectants  which  are  often 
recommended  to  purify  the  air  of  the  sick-room  are, 
at  the  most,  simply  deodorisers  of  greater  or  less 
value,  and  are  entirely  unreliable  for  the  destruction 
of  disease  germs  under  the  conditions  existing  in  an 
occupied  apartment. 

Disinfection  of  the  vacated  room  consists  in  the 
destruction  of  all  infectious  particles  which  remain 
attached  to  surfaces,  or  lodged  in  crevices,  in  inter- 
stices of  textile  fabrics,  etc.  The  object  in  view  may 
be  accomplished  by  thorough  washing  with  a  reliable 
disinfecting  solution,  but  many  sanitarians  think  it 
advisable  to  "  disinfect  the  room "  with  a  gaseous 
disinfectant,  such  as  formaldehyd  or  sulphur  dioxid. 
If  "  fumigation  "  with  sulphur  dioxid  is  resorted  to,  the 
directions  given  by  the  Committee  on  Disinfectants 
of  the  American  Public  Health  Association  should 
be  followed  :  that  is,  three  pounds  of  sulphur  should 
be  burned  for  every  thousand  cubic  feet  of  air-space. 
At  the  end  of  from  twelve  to  twenty-four  hours,  doors 
and  windows  should  be  opened,  and  the  room  freely 
ventilated.  After  this  fumigation,  all  surfaces  should 
be  washed  with  a  disinfecting  solution  (chloride  of 
lime  2  per  cent.,  carbolic  acid  2  percent.,  or  mercuric 
chloride  1:1000),  and  afterwards  thoroughly  scrubbed 
with  soap  and  hot  water.  Plastered  walls  should  be 
whitewashed. 


54  INFECTION  AND  IMMUNITY 

Experiments  made  during  the  past  twenty  years 
have  shown  that  fumigation  by  burning  sulphur  is  not 
by  any  means  so  reliable  a  method  of  disinfection  as 
was  formerly  supposed.  It  has  very  little  value  un- 
less the  articles  to  be  disinfected  are  in  a  moist  con- 
dition. This  may  be  effected  by  introducing  steam 
into  the  room  together  with  the  sulphur  fumes.  There 
is  a  class  of  diseases,  however,  in  which  sulphur  fumi- 
gation is  a  most  valuable  method  of  disinfection  :  I 
refer  to  yellow  fever  and  the  malarial  fevers,  in  which 
diseases  the  infectious  agent  is  transmitted  by  mos- 
quitoes. Such  mosquitoes,  after  filling  themselves 
with  blood  from  the  sick  person,  hang  about  the  room, 
attached  to  the  ceiling,  to  window-curtains,  etc.,  for 
the  purpose  of  digesting  their  meal  and  supplying 
themselves  with  another  when  occasion  offers.  The 
room  is  infected  because  of  the  presence  of  these 
infected  mosquitoes,  which  with  the  blood  of  the 
patient  have  taken  in  the  disease  germs  present  in 
such  blood.  Disinfection  in  such  a  case  consists  in 
the  destruction  of  the  infected  mosquitoes,  and  this  is 
very  readily  accomplished  by  means  of  sulphur  fumi- 
gation. Owing  to  the  superior  germicidal  power  of 
formaldehyd  and  its  non-toxic  properties,  this  gas  has 
to  a  considerable  extent  taken  the  place  of  sulphur 
fumigation  for  disinfecting  purposes. 

Formaldehyd  is  generated  either  by  the  application 


DISINFECTION  B  Y  GASES  55 

of  heat  to  an  aqueous  solution  of  the  gas  (formalin) 
or  by  the  oxidation  of  wood  alcohol. 

In  making  practical  use  of  this  agent  a  suitable 
apparatus  will  be  required.  For  the  disinfection  of  a 
room  with  its  contents,  freely  exposed  for  surface 
disinfection,  one  pound  of  formalin  should  be  volatil- 
ised for  each  thousand  cubic  feet  of  air-space — the 
time  of  exposure  to  the  disinfecting  action  of  the  gas 
being  not  less  than  twelve  hours.  In  the  absence  of 
any  apparatus  satisfactory  results  have  been  obtained 
by  the  Department  of  Health  of  the  city  of  Chicago, 
as  follows : 

"  Ordinary  bed  sheets  were  employed  to  secure  an  adequate 
evaporatory  surface,  and  these,  suspended  in  the  room,  were 
simply  sprayed  with  a  forty  per  cent,  solution  of  formalin  through 
a  common  watering-pot  rose-head.  A  sheet  of  the  usual  size 
and  quality  will  carry  from  one  hundred  and  fifty  to  one  hundred 
and  eighty  cc.  of  the  solution  without  dripping,  and  this  quantity 
has  been  found  sufficient  for  the  disinfection  of  one  thousand 
cubic  feet  of  space.  Of  course,  the  sheets  may  be  modified  to 
any  necessary  number.  .  .  .  Surface  disinfection  was  thorough, 
while  a  much  greater  degree  of  penetration  was  shown  than  that 
secured  by  any  other  method." 

Formalin  may  also  be  used  in  the  disinfection  of 
rooms  and  their  contents  by  spraying  all  exposed 
surfaces. 

Experiments  made  by  Kinyoun  and  others  show 
that  formaldehyd  gas  does  not  injure  the  colour  or 
textile  strength  of  fabrics  of  wool,  silk,  cotton  or  linen 


56  INFECTION  AND  IMMUNITY 

and  that  it  has  no  injurious  action  upon  furs,  leather, 
copper,  brass,  nickel,  zinc,  polished  steel  or  gilt  work. 
Iron  and  unpolished  steel  are  attacked  by  the  gas. 

As  is  the  case  with  sulphur  dioxid  the  germicidal 
power  of  formaldehyd  is  increased  by  the  presence 
of  moisture. 

Other  volatile  and  gaseous  disinfectants  have  been 
used,  but  from  a  practical  point  of  view  those  men- 
tioned are  the  best.  Chlorin  is  a  powerful  germi- 
cide in  the  presence  of  moisture,  but  its  irritant  and 
corrosive  properties  interfere  with  its  usefulness  as  a 
disinfecting  agent. 


CHAPTER   X 

VARIOUS  CHEMICAL  DISINFECTANTS 

TT  is  my  intention  in  the  present  chapter  to  refer 
briefly  to  some  of  the  most  useful  chemical  dis- 
infectants. The  most  potent  germicide  is  not  always 
the  best  disinfectant  for  practical  use.  Questions  of 
cost,  poisonous  properties,  injurious  effects  upon  tex- 
tile fabrics,  etc.,  must  be  considered  in  selecting  an 
agent  for  any  special  purpose. 

The  mineral  acids  are  all  active  germicides  when 
used  in  solutions  of  proper  strength,  and  a  one-per- 
cent, solution  of  sulphuric,  nitric,  or  hydrochloric  acid 
will  quickly  destroy  pathogenic  bacteria  in  the  absence 
of  spores.  Such  a  solution  could  be  safely  used  to 
disinfect  the  excreta  of  patients  suffering  from  cholera 
or  typhoid  fever.  Among  the  vegetable  acids  it  is 
only  necessary  to  mention  citric  acid,  which  has  been 
recently  recommended,  in  the  form  of  lemon  juice,  for 
destroying  typhoid  bacilli  in  drinking-water.  The 
idea  that  the  addition  of  a  spoonful  of  lemon-juice  to 

57 


58  INFECTION  AND  IMMUNITY 

a  glass  of  water,  just  before  drinking  it,  will  be  suf- 
ficient to  ensure  the  destruction  of  typhoid  bacilli 
present  in  the  water  is  not  well  founded.  Exact  ex- 
periments show  that  the  bacillus  of  typhoid  fever  is 
killed,  in  five  hours'  time,  by  a  solution  containing 
one-half  of  one  per  cent,  of  citric  acid.  But  the  time 
element  must  not  be  overlooked.  However,  the  ex- 
perimental evidence  supports  the  view  that  the  typhoid 
bacillus  or  the  cholera  spirillum  would  not  retain  their 
vitality  very  long  in  a  strong  lemonade,  containing 
one  per  cent,  or  more  of  citric  acid.  The  addition  of 
sulphurous  acid  to  water  is  still  more  effective,  espe- 
cially as  regards  the  cholera  germ,  which  is  very  sens- 
itive to  the  action  of  acids.  The  addition  of  this  acid 
to  drinking-water  during  the  prevalence  of  cholera 
has  been  recommended  and  practised,  apparently  with 
good  results.  It  has  been  shown  by  carefully  con- 
ducted experiments  that  one  part  in  five  hundred  will 
destroy  the  cholera  spirillum  in  the  course  of  a  few 
hours. 

The  caustic  alkalies  all  have  considerable  germicidal 
value.  Potash  soap  containing  an  excess  of  alkali 
will  destroy  the  typhoid  bacillus  in  six-per-cent.  so- 
lution within  thirty  minutes ;  and  the  scrubbing  of 
floors,  articles  of  furniture,  etc.,  with  such  a  solution, 
especially  when  used  hot,  is  a  most  reliable  method 
of  disinfection.  Solutions  of  potash — common  lye — 


VARIOUS  CHEMICAL  DISINFECTANTS         59 

or  of  soda  are  extremely  valuable  for  certain  purposes 
in  domestic  sanitation,  and  scientific  researches  fully 
justify  the  cleansing  methods  with  these  agents  which 
have  long  been  popular  with  good  housewives.  A 
hot  solution  of  caustic  soda  or  potash  in  the  propor- 
tion of  one  part  to  two  hundred  of  water  will  quickly 
destroy  the  germs  of  cholera,  of  typhoid  fever,  of 
diphtheria,  or  of  glanders. 

Caustic  lime  is  also  an  excellent  disinfectant  and 
has  the  advantage  of  being  comparatively  cheap.  For 
this  reason  it  is  one  of  the  best  agents  for  the  disinfec- 
tion of  masses  of  filth  in  vaults  or  cesspools  and  upon 
the  surface  of  the  ground.  Milk  of  lime,  made  by 
slaking  fresh  quicklime  with  water  and  mixing  the 
resulting  hydrate  of  lime  with  eight  parts  of  water 
may  be  used  for  this  purpose  and  also  for  the  dis- 
infection of  liquid  excreta  in  the  sick-room.  Lime 
wash  applied  to  surfaces  is  a  reliable  disinfectant,  as 
has  been  proved  by  experiment,  thus  giving  scientific 
confirmation  of  the  value  of  a  method  which  has 
gained  popular  favour  as  a  result  of  experience — that 
is,  of  the  sanitary  value  of  whitewash  freely  and  fre- 
quently applied  to  outbuildings,  cellar  walls,  etc. 

Various  coal-tar  products  have  been  proved  to  be 
valuable  germicides,  and  on  account  of  their  compar- 
ative cheapness  have  been  largely  used  in  practical 
disinfection.  Among  these  the  most  useful  are 


60  INFECTION  AND  IMMUNITY 

carbolic  acid,  creolin,  cresol,  and  lysol.  A  five-per-cent. 
solution  of  either  of  these  may  be  used  for  the  disin- 
fection of  the  liquid  discharges  of  patients  with  cholera, 
cholera  infantum,  dysentery,  or  typhoid  fever ;  also 
for  the  expectoration  of  those  suffering  from  pulmon- 
ary tuberculosis,  pneumonia,  diphtheria,  influenza, 
scarlet  fever,  measles,  or  whooping-cough.  It  must 
be  remembered,  however,  that  time  is  an  element  in 
the  accomplishment  of  disinfection,  and  after  adding 
the  disinfecting  solution  to  the  material  to  be  dis- 
infected an  interval  of  an  hour  or  more  should  be 
allowed  before  the  contents  of  the  vessel  are  thrown 
into  a  vault  or  sewer.  A  two-per-cent.  solution  of  one 
of  the  above  mentioned  disinfectants  may  be  used 
for  washing  floors,  articles  of  furniture,  leather,  etc. 
Such  a  solution  may  also  be  used  for  the  disinfec- 
tion of  pocket-handkerchiefs,  bed-linen,  underclothing, 
and  other  articles  which  require  disinfection  before 
sending  them  to  the  laundry.  The  articles  to  be  dis- 
infected should  be  completely  immersed  in  the  dis- 
infecting solution,  contained  in  a  suitable  receptacle, 
and  left  for  at  least  an  hour  before  removal  from  the 
sick-room  or  its  immediate  vicinity. 

Chlorinated  lime  ("  chloride  of  lime,"  "  bleaching 
powder  ")  is  a  valuable  disinfectant  and  also  a  prompt 
deodoriser.  It  may  be  used  for  the  disinfection  of 
excreta  in  the  sick-room,  in  open  pits,  etc.,  and  for 


VARIOUS  CHEMICAL  DISINFECTANTS          61 

infected  sputa.  A  solution  containing  six  ounces  of 
good  bleaching  powder  to  the  gallon  of  water  will  be 
suitable  for  ordinary  use.  By  exposure  to  the  air  the 
chloride  of  lime  rapidly  deteriorates  in  quality.  It 
should  therefore  be  kept  in  air-tight  receptacles,  and 
only  so  much  of  the  disinfecting  solution  made  as  is 
required  for  immediate  use.  Owing  to  its  bleaching 
properties  and  injurious  action  upon  fabrics  of  all 
kinds  the  chlorinated-lime  solution  is  seldom  used  for 
the  disinfection  of  bed-linen  and  articles  of  clothing, 
but  it  may  be  employed  for  washing  floors  and  other 
woodwork. 

Many  of  the  metallic  salts  have  decided  germicidal 
value,  and  some  of  them  have  been  largely  used  in 
practical  disinfection.  Among  these  the  bichloride 
of  mercury,  or  "  corrosive  sublimate,"  has  a  prominent 
place.  In  very  dilute  solutions  this  salt  is  fatal  to  all 
known  disease  germs,  and  in  the  proportion  of  i :  500 
it  will  destroy  the  spores  of  pathogenic  bacteria  (an- 
thrax, tetanus).  For  ordinary  use  a  standard  solu- 
tion of  one  part  in  one  thousand  parts  of  water  may 
be  used.  This  will  be  suitable  for  washing  surfaces 
and  for  the  disinfection  of  bed-  and  body-linen. 
But  owing  to  the  fact  that  the  bichloride  of  mercury 
combines  with  albuminous  substances,  and  is  thus 
rendered  practically  inert,  this  salt  is  not  a  reliable 
disinfectant  for  excreta  or  expectorated  matters.  The 


62  INFECTION  AND  IMMUNITY 

very  poisonous  nature  of  this  salt  must  be  constantly 
kept  in  mind  by  those  who  make  use  of  it  for  disinfect- 
ing purposes.  The  solution  is  colourless,  and  a  fatal 
dose  might  easily  be  mistaken  for  water.  To  avoid 
such  accident  it  is  customary  to  colour  the  solution 
with  indigo  or  an  anilin  dye. 

Sulphate  of  copper  has  been  used  to  some  extent, 
especially  in  France,  for  the  same  purposes  as  the 
salt  last  mentioned  (corrosive  sublimate).  Its  germ- 
icidal  value  is  considerably  less,  but  in  solutions  con- 
taining from  two  or  five  per  cent,  it  is  reliable  for 
the  destruction  of  pathogenic  bacteria  not  containing 
spores.  Like  the  bichloride  of  mercury  its  germicidal 
action  is  neutralised  to  a  considerable  extent  by  the 
presence  of  albuminous  material.  It  is  therefore  not 
to  be  selected  for  the  disinfection  of  sputa  and  excreta. 

With  reference  to  the  various  proprietary  disinfect- 
ants which  are  in  the  market  and  largely  used,  I 
would  say  that  many  of  them  are  deodorants  of  more 
or  less  value  and  are  entirely  unreliable  for  the  de- 
struction of  disease  germs.  Others  contain  germ- 
icidal agents  of  value  ;  but,  as  a  rule,  they  are  not 
economical  in  use,  as  compared  with  heat,  carbolic 
acid,  formaldehyd,  and  other  disinfectants  of  estab- 
lished value  referred  to  in  the  present  volume. 


CHAPTER  XI 

NATURAL  IMMUNITY 

IT  is  hardly  necessary  to  explain  that  absence  of 
susceptibility  to  an  infectious  disease  constitutes 
what  is  known  as  immunity  for  or  against  the  disease 
in  question.  Now  this  immunity  may  be  natural  or 
acquired — that  is,  due  to  inheritance  or  developed  in 
a  susceptible  individual  subsequent  to  birth.  We 
have  said  in  a  preceding  chapter  that  man  is  immune 
as  regards  certain  infectious  diseases  of  the  lower  ani- 
mals, and  that  many  of  the  infectious  diseases  to 
which  he  is  subject  are  not  transmitted  to  the  domes- 
tic animals  with  which  he  is  most  closely  associated. 
This  natural  immunity  is  not,  however,  in  all  cases 
absolute  and  complete.  For  example,  the  white  rat 
possesses  a  remarkable  immunity  against  anthrax,  a 
disease  which  may  be  communicated  by  inoculation 
to  sheep,  cattle,  rabbits,  guinea-pigs,  mice,  and  to  man 
himself.  But  it  has  been  shown  that  this  natural  im- 
munity of  the  white  rat  may  be  overcome  by  giving 

63 


64  INFECTION  AND  IMMUNITY 

it  an  exclusively  vegetable  diet.  Again,  natural  im- 
munity may  in  some  cases  be  overcome  by  the  de- 
vitalising agencies  mentioned  in  the  chapter  on  sus- 
ceptibility to  infection  (starvation,  great  fatigue,  etc.). 
Infection  also  depends  upon  the  comparative  virul- 
ence of  the  infecting  agent,  or  germ,  and  to  some 
extent  upon  the  number  of  germs  introduced. 

Immunity,  therefore,  whether  natural  or  acquired, 
often  has  only  a  relative  value,  and  may  be  overcome 
as  a  result  of  circumstances  favourable  to  infection. 
Thus  it  has  been  found  that  germs  having  very  little 
pathogenic  virulence,  and  harmless  under  ordinary 
conditions,  may  kill  guinea-pigs  when  injected  into 
the  muscles  of  the  thigh  after  they  have  been  bruised 
by  mechanical  violence.  Pasteur  found  that  fowls, 
which  have  a  natural  immunity  against  anthrax,  be- 
come infected  and  die  if  they  are  subjected  to  artificial 
refrigeration  after  inoculation.  Pigeons  have  a  natural 
immunity  against  anthrax,  but  if  they  are  enfeebled 
by  lack  of  food  they  succumb  to  inoculations  with 
the  anthrax  bacillus. 

The  pathogenic  power  of  known  disease  germs 
also  varies  greatly  as  a  result  of  conditions  relating 
to  their  development.  In  general  it  may  be  said  that 
cultivation  in  the  bodies  of  susceptible  animals  in- 
creases the  virulence  of  disease  germs.  Attenuation 
of  virulence  may  be  effected  by  several  methods,  all 


NATURAL  IMMUNITY  65 

of  which  depend  upon  subjecting  the  germs  to  preju- 
dicial influences  of  one  kind  or  another — long  exposure 
to  oxygen,  exposure  to  a  temperature  a  little  short  of 
that  which  would  completely  destroy  their  vitality, 
exposure  to  various  chemical  agents. 

Attenuated  germs  may  cause  infection  in  very  sus- 
ceptible animals,  and  may  gain  in  virulence  as  a  re- 
sult of  their  growth  in  such  animals.  After  passing 
through  a  series  of  susceptible  animals  they  may 
finally  acquire  such  pathogenic  virulence  that  they 
can  overcome  the  resisting  power  of  animals  having 
a  considerable  degree  of  natural  immunity.  Apply- 
ing the  facts  ascertained  by  experiments  upon  the 
lower  animals,  we  can  understand  how  the  earlier 
cases  in  an  epidemic  may  occur  in  the  most  suscept- 
ible individuals,  and  are  often  comparatively  mild  ; 
but,  as  a  result  of  its  transmission  through  a  series 
of  individuals,  the  germ  gradually  increases  in  vir- 
ulence and  the  epidemic  in  malignancy.  Thus  the 
earlier  cases  in  an  epidemic  of  diphtheria  or  of  scarlet 
fever  are  often  mild,  while  later  cases  prove  to  be 
extremely  difficult  to  manage  and  show  a  high  rate  of 
mortality. 

Infection  also  depends  to  some  extent  upon  the 
number  of  germs  introduced.  The  resources  of  na- 
ture, upon  which  immunity  depends,  may  be  suffi- 
cient to  dispose  of  a  few  typhoid  bacilli  or  diphtheria 


66  INFECTION  AND  IMMUNITY 

bacilli ;  while  a  larger  number  introduced  at  one  time 
may  overwhelm  the  resisting  power  of  the  individual. 

The  essential  difference  between  a  susceptible  and 
immune  animal  depends  upon  the  fact  that  in  one 
the  pathogenic  germ,  when  introduced  by  accident  or 
experimental  inoculation,  multiplies  and  invades  the 
tissues  or  the  blood,  where,  by  reason  of  its  nutritive 
requirements  and  toxic  products,  it  produces  changes 
in  the  tissues  and  fluids  of  the  body  which  constitute 
disease  and  may  result  in  death.  On  the  other  hand, 
in  an  immune  animal  multiplication  of  the  germ  and 
consequent  disturbance  of  vital  functions  does  not 
occur,  or  is  restricted  to  a  local  invasion  of  limited 
extent,  in  which  the  parasitic  invader  soon  succumbs 
to  the  resources  of  nature.  This  essential  difference 
evidently  depends  upon  conditions  favourable  or  un- 
favourable to  the  development  of  the  germ  ;  or  upon 
its  destruction  by  some  active  agent  present  in  the 
tissues  or  fluids  of  the  body  of  the  immune  individ- 
ual ;  or  upon  a  neutralisation  of  its  toxic  products 
by  some  substance  in  the  body  of  the  animal  which 
resists  infection. 

Among  the  unfavourable  conditions  which  may 
be  supposed  to  prevent  the  development  of  disease 
germs  in  animals  which  have  a  natural  immunity 
against  infection  by  them,  we  may  mention,  first,  the 
temperature  of  the  animal.  It  is  well  known  that 


NATURAL  IMMUNITY  67 

the  constant  body  temperature  of  mammals  varies 
considerably  for  different  species.  Birds,  as  a  rule, 
have  a  higher  temperature  than  mammals,  and  rep- 
tiles are  "  cold-blooded  animals."  A  disease  germ, 
like  the  tubercle  bacillus,  for  example,  which  requires 
for  its  development  a  temperature  not  very  different 
from  that  of  a  healthy  man,  may  fail  to  infect  a 
pigeon  because  of  its  comparatively  high,  or  a  frog 
because  of  its  low,  temperature.  Certain  experiments 
which  have  been  made  by  bacteriologists  give  sup- 
port to  this  view.  This  is  the  explanation  offered 
by  Pasteur  of  the  immunity  of  fowls  against  anthrax 
—  a  disease  of  sheep  and  cattle  ;  and  in  support  of 
this  view  he  showed  by  experiment  that  when  chick- 
ens are  refrigerated  by  being  immersed  in  cold 
water,  after  inoculation,  they  are  liable  to  become 
infected  and  to  die.  Again,  the  composition  and 
especially  the  reaction  of  the  blood  and  other  body 
fluids  may  perhaps  be  the  determining  factor.  Some 
germs  do  not  grow  readily  in  an  alkaline  medium ; 
and  some  animals  —  for  example,  the  white  rat- 
have  a  highly  alkaline  blood.  Experiments  made  by 
the  German  bacteriologist,  Behring,  seem  to  show 
that  the  natural  immunity  of  the  white  rat  against 
anthrax  infection  is  lost  when  the  animal  is  given 
food  which  reduces  the  alkalinity  of  its  blood.  It 
is  probable,  also,  that  the  presence  or  absence  of 


68  INFECTION  AND  IMMUNITY 

various  substances  favourable  or  unfavourable  to  the 
development  of  particular  disease  germs  may,  in  cer- 
tain cases,  be  the  fundamental  cause  of  race  immun- 
ity. It  has  been  shown  by  experiment  that  natural 
immunity  may  be  overcome  in  certain  animals  by 
inoculating  them  with  disease  germs  mixed  with 
certain  chemical  substances  —  or  with  sterilised  cult- 
ures of  various  bacteria.  The  susceptibility  of  the 
victims  of  chronic  alcoholism  to  infection  by  various 
pathogenic  bacteria  is  well  known.  Whether  this  is 
due  to  the  presence  of  alcohol  or  to  chemical  changes 
in  the  body  fluids  resulting  from  its  use  is  not  de- 
termined. A  complete  knowledge  of  the  facts  would 
probably  show  that  immunity,  natural  or  acquired,  in 
the  ultimate  analysis,  to  a  large  extent  has  a  chemical 
basis  —  that  is,  it  depends  upon  the  presence  of  some 
substance  which  exercises  a  deleterious  influence 
upon  the  germ  or  neutralises  its  toxic  products. 

That  the  blood-serum  of  healthy  animals  contains 
substances  which  have  a  decided  germicidal  effect 
has  been  demonstrated  by  experiments  made  with 
blood  withdrawn  from  the  circulation.  This  property 
belongs  to  the  clear  serum  which  is  obtained  after 
coagulation  of  the  fibrin  and  separation  of  the  clot 
containing  the  red  and  white  blood  corpuscles.  When 
the  blood-serum  is  kept  for  some  time  it  loses  its 
germicidal  activity.  This  is  also  destroyed  by  heat, 


NATURAL  IMMUNITY  69 

but  not  by  freezing.  The  blood  of  different  species 
differs  considerably  in  this  regard,  and  that  of  the 
same  species  may  show  a  decidedly  greater  germ- 
icidal  action  for  one  disease  germ  than  for  others. 
That  the  presence  of  these  germicidal  substances  con- 
stitutes a  most  important  element  in  natural  immun- 
ity can  scarcely  be  doubted.  According  to  Behring 
the  blood  of  the  rat  and  of  the  frog,  which  an- 
imals have  a  natural  immunity  against  anthrax,  is 
especially  fatal  to  the  anthrax  bacillus.  The  numer- 
ous experiments  which  have  been  made  show  that 
the  germicidal  action  of  blood-serum,  which  is  very 
promptly  manifested,  is  limited  as  to  the  number  of 
bacteria  which  may  be  destroyed  by  a  given  amount. 
When  the  number  of  bacteria  is  excessive  only  a 
limited  number  are  destroyed,  and  after  an  interval 
those  not  destroyed  multiply  abundantly  in  the  blood- 
serum,  which,  in  the  absence  of  its  germicidal  con- 
stituent, is  an  excellent  culture  medium  for  many 
pathogenic  bacteria. 

It  would  appear  from  this  that  the  element  in  the 
blood  to  which  the  germicidal  action  is  due  is  neu- 
tralised in  exercising  this  power — in  other  words, 
that  the  effect  is  the  result  of  a  chemical  reaction. 
These  germicidal  substances  in  the  blood  of  healthy 
animals  are  complex  nitrogenous  compounds,  which 
belong  to  the  group  of  organic  bodies  known  to 


70  INFECTION  AND  IMMUNITY 

chemists  as  proteids.  They  are  sometimes  spoken 
of  as  "  defensive  proteids,"  because  they  appear  to 
serve  as  a  provision  of  nature  for  defence  against 
disease  germs.  Possibly  the  increased  susceptibility 
to  infection  resulting  from  starvation,  great  fatigue, 
and  other  devitalising  agencies  is  due  to  a  diminution 
in  the  quantity  of  these  defensive  proteids  present  in 
the  blood.  These  germicidal  substances  differ  from 
the  "  antitoxins,"  of  which  I  shall  speak  in  a  subse- 
quent chapter,  in  the  fact  that  their  power  to  destroy 
pathogenic  bacteria  is  destroyed  by  a  comparatively 
low  temperature  (140°  Fahr.).  Independent  re- 
searches made  by  several  different  investigators  seem 
to  show  that  the  defensive  proteids  of  the  blood  have 
their  origin  in  the  leucocytes,  or  white  blood-cor- 
puscles, and  that  an  alkaline  condition  of  the  blood  is 
favourable,  if  not  essential,  to  the  formation  of  such 
germicidal  substances,  or  at  least  to  their  release  from 
the  leucocytes.  The  number  of  leucocytes  increases 
in  certain  infectious  diseases,  and  this  increase, 
together  with  an  increased  alkalinity  of  the  blood, 
which  has  been  noted,  may  be  a  provision  of 
nature  for  overcoming  infection  when  it  has  already 
occurred. 

A  more  direct  role  has  been  ascribed  to  the  leu- 
cocytes as  defenders  of  the  living  body  against 
invasion  by  pathogenic  bacteria. 


NATURAL  IMMUNITY  71 

In  my  chapter  on  "  Bacteria  in  Infectious  Diseases," 
in  Bacteria,  published  in  the  spring  of  1884,  but 
placed  in  the  hands  of  the  publishers  in  1883,  I  say : 

"Jf  we  add  a  small  quantity  of  culture  fluid  containing  the 
bacteria  of  putrefaction  to  the  blood  of  an  animal,  withdrawn 
from  the  circulation  into  a  proper  receptacle,  and  maintained  in 
a  culture  oven  at  blood-heat,  we  shall  find  that  these  bacteria 
multiply  abundantly,  and  evidence  of  putrefactive  decomposition 
will  soon  be  perceived.  But  if  we  inject  a  like  quantity  of  the 
culture  fluid,  with  its  contained  bacteria,  into  the  circulation  of 
a  living  animal,  not  only  does  no  increase  and  no  putrefactive 
change  occur,  but  the  bacteria  introduced  quickly  disappear, 
and  at  the  end  of  an  hour  or  two  the  most  careful  microscopical 
examination  will  not  reveal  the  presence  of  a  single  bacterium. 
This  difference  we  ascribe  to  the  vital  properties  of  the  fluid  as 
contained  in  the  vessels  of  a  living  animal,  and  it  seems  probable 
that  the  little  masses  of  protoplasm  known  as  white  blood-cor- 
puscles are  the  essential  histological  elements  of  the  blood,  so 
far  as  any  manifestation  of  vitality  is  concerned.  The  writer 
has  elsewhere  (1881)  suggested  that  the  disappearance  of  the  bacteria 
from  the  circulation,  in  the  experiments  referred  to,  may  be  effected 
by  the  white  corpuscles,  which,  it  is  well  known,  pick  up,  after  the 
manner  of  amoebae,  any  particles,  organic  or  inorganic,  which 
come  in  their  way.  And  it  requires  no  great  stretch  of  credulity 
to  believe  that  they  may,  like  an  am&ba,  digest  and  assimilate  the  pro- 
toplasm of  the  captured  bacterium,  thus  putting  an  end  to  the  possi- 
bility of  its  doing  any  harm. 

"  In  the  case  of  a  pathogenic  organism  we  may  imagine  that, 
when  captured  in  this  way,  it  may  share  a  like  fate  if  the  captor 
is  not  paralysed  by  some  potent  poison  evolved  by  it,  or  over- 
whelmed by  its  superior  vigour  and  rapid  multiplication.  In  the 
latter  event  the  active  career  of  our  conservative  white  corpuscles 
would  be  quickly  terminated,  and  their  protoplasm  would  serve 
as  food  for  the  enemy.  It  is  evident  that  in  a  contest  of  this  kind 
the  balance  of  power  would  depend  upon  circumstances  relating 


72  INFECTION  AND  IMMUNITY 

to  the  inherited  vital  characteristics  of  the  invading  parasite  and 
of  the  invaded  leucocyte." 

This  explanation  is  now  very  commonly  spoken  of 
as  the  "  Metschnikoff  theory,"  although,  as  shown,  by 
the  above  quotations,  it  was  clearly  stated  by  the 
writer  several  years  (1881)  before  Metschnikoff's  first 
paper  (1884)  was  published.  Metschnikoff  has,  how- 
ever, been  the  principal  defender  of  this  explanation 
of  acquired  immunity,  and  has  made  extensive  and 
painstaking  researches,  as  a  result  of  which  many 
facts  have  been  brought  to  light  which  appear  to 
give  support  to  this  theory. 

The  recorded  experimental  evidence  leads  us  to 
the  conclusion  that  natural  immunity  is  partly  due 
to  germicidal  substances  present  in  the  blood-serum, 
which  have  their  origin  in  the  leucocytes,  and  are 
soluble  only  in  an  alkaline  medium  ;  that  local  infec- 
tion is  usually  resisted  by  an  afflux  of  leucocytes  to 
the  point  of  invasion,  which  to  some  extent  serve  to 
protect  the  individual  from  disease  germs,  by  their 
direct  action  as  "  phagocytes"-—  that  is,  by  picking 
up  and  destroying  the  invading  parasites.  These 
agencies,  together  with  conditions  relating  to  body 
temperature,  and  the  chemical  constitution  of  the 
fluids  and  tissues  of  the  body  constitute  the  principal 
factors  upon  which  natural  immunity  depends. 


CHAPTER  XII 

ACQUIRED  IMMUNITY 

IT  is  well  known  that  in  certain  infectious  diseases  a 
single  attack  protects  the  individual  from  subse- 
quent attacks.  In  some  cases  such  protection  lasts 
during  life,  while  in  others  it  is  more  or  less  temporary. 

The  protection  afforded  by  an  attack  not  only 
varies  in  different  diseases,  but  in  the  same  disease 
differs  greatly  in  individual  cases.  Thus  second  or 
even  third  attacks  of  smallpox  occasionally  occur, 
although,  as  a  rule,  a  single  attack  is  protective. 

In  certain  diseases  second  attacks  are  not  infre- 
quent. This  is  true  of  pneumonia,  Asiatic  cholera, 
diphtheria,  and  especially  of  influenza.  But  there  is 
usually  a  considerable  interval  between  two  attacks 
of  any  of  these  diseases,  and  the  inference  is  that 
temporary  immunity  results  from  each  attack.  In 
the  malarial  fevers,  which  are  due  to  infection  by  a 
blood  parasite  of  a  different  class,  no  immunity  is 
afforded  by  an  attack  of  the  disease,  in  its  usual  form 

73 


74  INFECTION  AND  IMMUNITY 

at  least — chills  and  fever.  On  the  other  hand,  the 
debility  resulting  from  an  attack  seems  to  constitute 
a  predisposition  to  subsequent  attacks. 

As  showing  the  liability  to  two  or  more  attacks 
from  certain  infectious  diseases,  I  give  below  a  table 
compiled  from  the  literature,  as  given  in  medical 
journals,  which  was  published  several  years  ago 
(Maiselis). 

Second  Third  Fourth 

attacks.  attacks.  attacks. 

Smallpox  505  9  o 

Scarlet  fever  29  4  o 

Measles  36  i  o 

Typhoid  fever  202  5  i 

Cholera  29  3  2 

These  figures  support  the  view  generally  enter- 
tained by  physicians,  that  second  attacks  of  measles 
are  comparatively  rare,  while  second  attacks  of  small- 
pox are  not  infrequently  observed.  Considering  the 
large  number  of  cases  of  typhoid  fever  which  occur 
annually  in  all  parts  of  Europe  and  America,  the 
number  of  second  attacks  reported  is  comparatively 
small,  and  in  this  disease  it  may  be  stated  that,  as  in 
smallpox  and  scarlet  fever,  a  single  attack  usually 
protects  during  life  from  subsequent  attacks. 

The  second  attacks  of  cholera  recorded  are  not 
numerous,  but  an  investigation  made  in  the  countries 
where  this  disease  prevails  annually,  or  frequently, 
would  probably  show  that  two  or  more  attacks  of  the 


ACQUIRED  IMMUNITY  75 

disease  in  the  same  individuals  are  not  of  infrequent 
occurrence. 

That  immunity  may  result  from  a  comparatively 
mild  attack  as  well  as  from  a  severe  one  is  a  matter 
of  common  observation  in  the  case  of  smallpox, 
scarlet  fever,  yellow  fever,  measles,  and  other  infec- 
tious diseases.  And  it  not  infrequently  happens  that 
such  mild  attacks  are  not  recognised. 

In  that  case  the  protection  afforded  during  sub- 
sequent epidemics  is  often  ascribed  to  natural  im- 
munity. This  is  no  doubt  the  true  explanation  of 
the  immunity  of  natives  of  Havana,  and  other  cities 
where  yellow  fever  has  prevailed  for  many  years,  to 
this  disease.  An  unrecognised  attack  suffered  during 
childhood  has  resulted  in  immunity  which  is  supposed 
to  be  due  to  inheritance.  The  popular  idea  that 
natives  are  exempt  from  this  disease  is  an  additional 
motive  for  calling  it  by  some  other  name,  especially 
as  the  attacks  are  usually  extremely  mild  in  native- 
born  children. 

The  production  of  immunity  by  protective  inocula- 
tions was  for  a  long  time  limited  to  a  single  disease — 
smallpox.  Inoculations  with  virus,  obtained  from  a 
pustule  on  a  smallpox  patient,  were  extensively  prac- 
tised before  the  discovery  of  vaccination  by  Jenner. 
These  inoculations  gave  rise  to  a  mild  attack  of  the 
disease,  followed  by  immunity,  which  was  apparently 


76  INFECTION  AND  IMMUNITY 

as  complete  as  that  following  a  more  severe  attack 
contracted  in  the  usual  way.  This  method  seems  to 
have  been  practised  by  Eastern  nations  long  before  it 
\vas  introduced  into  Europe.  It  was  extensively  em- 
ployed in  Turkey  early  in  the  eighteenth  century,  and 
was  introduced  into  England  through  the  influence 
of  Lady  Mary  Wortley  Montagu.  No  doubt  the 
mortality  from  smallpox  was  greatly  diminished  by 
these  inoculations  ;  but  they  were  attended  by  the 
disadvantage  that  the  disease  was  propagated  by 
them,  inasmuch  as  inoculated  individuals  became  a 
source  of  infection  for  others.  Inoculation  was  still 
practised  in  England  for  some  time  after  the  demon- 
stration of  the  protective  value  of  vaccination,  but  in 
1840  it  was  prohibited  by  an  act  of  Parliament. 

There  is  some  evidence  that  vaccination  as  a  pro- 
tection against  smallpox  was  practised  to  a  limited 
extent  prior  to  the  time  of  Jenner.  Thus  Humboldt 
has  stated  that  it  was  known  at  an  early  period  to  the 
Mexicans.  But  its  introduction  as  a  reliable  method 
of  protecting  against  smallpox  is  due  to  the  patient 
researches  of  the  renowned  English  physician,  whose 
attention  was  first  attracted  to  the  subject  in  1 768, 
although  it  was  not  until  1796  that  he  made  his  first 
vaccination  in  the  human  subject.  His  first  public 
institution  for  the  practice  of  vaccination  was  estab- 
lished in  1799,  and  the  following  year  the  practice 


ACQUIRED  IMMUNITY  77 

was  introduced  into  France,  Germany,  and  the  United 
States. 

In  the  infectious  disease  of  cattle  known  as  pleuro- 
pneumonia,  protective  inoculations  were  successfully 
made  some  time  before  the  demonstration  by  Pasteur 
of  the  efficacy  of  such  noculations  in  anthrax  and 
chicken  cholera  (1880).  Various  methods  have  been 
employed.  The  natives  of  the  banks  of  the  Zam- 
beze  cause  animals  to  swallow  a  certain  quantity  of 
the  liquid  from  the  pleural  cavity  of  an  animal  re- 
cently dead,  and  thus  give  them  immunity.  The 
virus  has  been  injected  into  the  circulation  by  some 
experimenters,  and  others  have  proposed  to  attenuate 
it  by  heat.  But  the  method  which  has  been  most 
extensively  employed  is  that  discovered  by  the  Dutch 
settlers  at  the  Cape  of  Good  Hope  (the  Boers),  and 
consists  in  inoculating  animals  in  the  tail  with  serum 
from  the  lungs  of  an  animal  recently  dead,  or  with  a 
virus  obtained  from  the  tumefaction  produced  by 
such  an  inoculation  in  the  tail.  This  is  also  the 
method  most  extensively  employed  in  Australia,  into 
which  country  infectious  pleuro-pneumonia  was  intro- 
duced in  1858. 

Toussaint,  a  pioneer  in  researches  relating  to  pro- 
tective inoculations,  has  a  short  paper  in  the  Comp- 
tes  rendus  of  the  French  Academy  of  Sciences  of 
July  12,  1880,  entitled  "Immunity  from  Anthrax 


78  INFECTION  AND  IMMUNITY 

('charbon')  Acquired  as  a  Result  of  Protective  In- 
oculations." 

In  this  communication,  he  reports  his  success  in 
conferring  immunity  upon  five  sheep  by  means  of 
protective  inoculations,  and  also  upon  four  young 
dogs.  We  must,  therefore,  accord  him  the  priority 
in  the  publication  of  experimental  data  demonstrating 
the  practicability  of  accomplishing  this  result. 

But  it  is  especially  to  the  experimental  researches 
of  Pasteur  that  we  are  indebted  for  the  development 
of  practical  methods,  which  have  been  extensively 
employed  in  protecting  cattle,  sheep,  and  swine  from 
the  fatal  effects  of  various  infectious  maladies,  and 
man  from  hydrophobia  as  the  result  of  the  bite  of 
a  rabid  animal. 

Pasteur's  inoculations  are  made  with  an  "  attenu- 
ated virus  " — that  is,  with  a  culture  of  a  pathogenic 
micro-organism  which  has  a  diminished  degree  of 
virulence  and  which  whei  introduced  into  a  suscep- 
tible animal  induces  a  non-fatal  and  comparatively 
mild  attack. 

The  researches  of  Pasteur  and  of  his  followers  in 
this  line  of  investigation  show  that  pathogenic  viru- 
lence may  be  attenuated  by  prolonged  exposure  to 
oxygen  ;  by  exposure  to  a  temperature  a  little  below 
that  which  would  completely  destroy  vitality ;  by 
the  action  of  certain  chemical  agents  ;  and,  in  some 


ACQUIRED  IMMUNITY  79 

cases,  by  passing  through  a  series  of  non-susceptible 
animals. 

As  a  general  rule,  pathogenic  virulence  is  increased 
by  successive  inoculations  in  susceptible  animals  and 
diminished  by  cultivating  the  pathogenic  micro-organ- 
ism in  artificial  media  outside  of  the  animal  body,  or 
by  passing  it  through  animals  having  but  slight  sus- 
ceptibility to  its  pathogenic  action.  As  pathogenic 
virulence  depends,  to  a  considerable  extent  at  least, 
upon  the  formation  of  toxic  substances  during  the 
active  development  of  the  pathogenic  micro-organism, 
we  infer  that  diminished  virulence  is  due  to  a  dimin- 
ished production  of  these  toxic  substances. 

An  important  step  was  made  in  the  progress  of  our 
knowledge  in  this  field  of  research  when  it  was  shown 
that  animals  may  be  made  immune  against  certain 
infectious  diseases  by  inoculating  them  with  filtered 
cultures  containing  the  toxic  substances  just  referred 
to,  but  free  from  the  living  bacteria  to  which  they 
owe  their  origin.  The  first  satisfactory  experimental 
evidence  of  this  important  fact  was  obtained  by  Sal- 
mon and  Smith  in  1886.  These  bacteriologists  suc- 
ceeded in  producing  an  immunity  in  pigeons  against 
the  pathogenic  effects  of  the  bacillus  of  hog  cholera, 
which  is  very  fatal  to  these  birds,  by  inoculating  them 
with  sterilised  cultures  of  the  bacillus  mentioned. 
Similar  results  were  reported  by  Roux  in  1888,  from 


8o  INFECTION  AND  IMMUNITY 

the  injection  into  susceptible  animals  of  sterilised 
cultures  of  the  anthrax  bacillus.  More  recently  (1890) 
Behring  and  Kitasato  have  shown  that  animals  may 
be  made  immune  against  the  pathogenic  action  of 
the  bacillus  of  tetanus  or  the  bacillus  of  diphtheria 
by  the  injection  of  filtered,  germ-free  cultures  of  these 
bacilli. 

In  Pasteur's  protective  inoculations  against  hydro- 
phobia, it  is  probable  that  the  immunity  which  is  de- 
veloped after  infection  by  the  bite  of  a  rabid  animal 
is  due  to  the  toxin  of  this  disease  present  in  the 
emulsion  of  spinal  cord  which  is  used  in  these  in- 
oculations. 

We  have  also  experimental  evidence  that  animals 
may  acquire  an  artificial  immunity  against  certain 
poisonous  substances  of  animal  and  vegetable  origin. 

By  inoculations  with  minute  and  gradually  increas- 
ing doses,  animals  may  be  made  immune  against  rattle- 
snake venom,  and  there  is  reason  to  believe  that 
persons  who  have  been  repeatedly  stung  by  poison- 
ous insects — mosquitoes,  bees — acquire  a  considerable 
degree  of  immunity  from  the  distressing  local  effects 
of  their  stings. 

Professor  Ehrlich,  of  Berlin,  in  1891,  published  the 
results  of  some  researches  which  have  an  important 
bearing  upon  the  explanation  of  acquired  immunity, 
and  which  show  that  susceptible  animals  may  be 


ACQUIRED  IMMUNITY  81 

made  immune  against  the  action  of  certain  toxic  pro- 
teids  of  vegetable  origin,  other  than  those  produced 
by  bacteria, — one,  ricin,  from  the  castor-oil  bean,  the 
other,  abrin,  from  the  jequirity  bean.  The  toxic  po- 
tency of  ricin  is  somewhat  greater  than  that  of  abrin, 
but  both  are  far  more  poisonous  than  strychnin.  A 
small  quantity  of  a  solution  containing  one  part  in 
one  hundred  thousand  parts  of  water  will  quickly  kill 
a  mouse.  But  when  injected  into  these  animals  in 
still  smaller  and  non-fatal  doses,  or  given  to  them 
with  their  food,  immunity  may  be  established  to  such 
a  degree  that  they  resist  subcutaneous  injections  of 
two  hundred  to  four  hundred  times  the  quantity  re- 
quired to  kill  a  non-immune  animal. 

In  a  later  paper  (1892),  Ehrlich  has  given  an  account 
of  subsequent  experiments  which  show  that  the  young 
of  mice,  which  have  an  acquired  immunity  for  these 
vegetable  poisons,  acquire  immunity  from  the  inges- 
tion  of  their  mother's  milk ;  and  also  that  immunity 
from  tetanus  may  be  acquired  in  a  brief  time  by 
young  mice  through  their  mother's  milk. 

These  results  have  been  confirmed  by  other  observ- 
ers and  show  that  some  substance  upon  which  ac- 
quired immunity  depends  is  present  in  the  milk  of  an 
immune  animal. 


CHAPTER  XIII 

ANTITOXINS 

\  A  7"E  have  seen  in  the  preceding  chapter  that,  in 
certain  cases  at  least,  acquired  immunity  is 
due  to  the  presence  of  substances  developed  in  the 
body  of  the  immune  animal  which  may  escape  in  the 
milk  of  a  nursing  female  and  give  protection  to  its 
young.  Such  protective  substances  are  called  "  anti- 
toxins," because  it  is  evident  that  they,  in  some  way, 
neutralise  the  toxins  of  various  disease  germs  and 
the  animal  and  vegetable  poisons  referred  to — abrin, 
ricin,  snake-venom. 

The  German  chemists,  Brieger  and  Ehrlich,  have 
succeeded  in  separating  the  antitoxin  of  tetanus 
from  the  milk  of  a  goat  which  had  been  made  im- 
mune by  repeated  inoculations  with  the  toxic  pro- 
ducts of  the  tetanus  bacillus.  A  precipitate  obtained 
from  the  milk  by  chemical  processes  proved  to  be 
from  four  hundred  to  six  hundred  times  as  active  as 
the  milk  itself,  as  shown  by  its  power  to  neutralise 

82 


ANTITOXINS  83 

the  tetanus  toxin.  But  the  usual  source  from  which 
antitoxins  are  obtained  for  practical  purposes  is  the 
blood  of  animals  which  have  been  rendered  immune. 
The  diphtheria  antitoxin,  which  is  now  extensively 
and  successfully  employed  for  the  cure  of  diphtheria, 
is  obtained  from  the  blood  of  horses  which  have  been 
immunised  by  repeated  inoculations  with  the  toxic 
products  of  the  diphtheria  bacillus. 

A  most  interesting  question  presents  itself  in  con- 
nection with  the  discovery  of  the  antitoxins :  Is  the 
animal  which  has  been  immunised  against  any  par- 
ticular toxin  also  immune  for  other  poisonous  sub- 
stances of  the  same  class  ?  This  question  has  been 
definitely  answered  in  the  negative  by  experimental 
investigation.  In  other  words,  each  specific  toxin 
causes  the  development  in  the  body  of  the  immune 
animal  of  a  specific  antitoxin  which  has  no  neutralis- 
ing action  upon  any  other  toxin  than  that  which  gave 
rise  to  its  production.  An  animal  which  has  been 
immunised  against  the  toxic  action  of  ricin  is  poi- 
soned by  the  usual  fatal  dose  of  abrin.  The  tetanus 
antitoxin  affords  no  protection  against  the  poisonous 
products  of  the  diphtheria  bacillus  and  vice  versa. 

The  antitoxins  protect  susceptible  animals  from  in- 
fection when  introduced  by  inoculation  at  the  same 
time  or  in  advance  of  the  disease  germs  against 
which  they  have  a  specific  action.  They  may  also,  in 


84  INFECTION  AND  IMMUNITY 

some  cases,  be  successfully  used  in  the  cure  of  infec- 
tious diseases,  when  these  have  not  advanced  too  far. 
The  remarkable  success  attending  the  use  of  the 
diphtheria  antitoxin  for  this  purpose  is  well  known 
and  a  certain  degree  of  success  has  attended  the 
efforts  of  physicians  in  the  treatment  of  other  dis, 
eases  by  the  same  method — tetanus,  erysipelas,  pneu- 
monia. But  specific  treatment  by  antitoxins  is  still 
in  its  infancy  and  much  careful  experimental  work 
and  clinical  experience  will  be  necessary  in  order  to 
determine  the  practical  value  of  this  method  in  the 
diseases  mentioned  and  in  other  infectious  maladies. 
Enough  is  known  at  present,  however,  to  lead  to 
the  hope  that  when  methods  have  been  devised  for 
obtaining  these  various  antitoxins  in  a  pure  and  con- 
centrated form  they  will  constitute  a  most  valuable 
addition  to  our  resources  for  the  treatment  of  infectious 
diseases.  Indeed  the  only  hope  of  specific  medication 
for  such  diseases  appears  to  lie  in  this  direction. 

In  the  present  volume  I  shall  not  attempt  to  dis- 
cuss the  questions  connected  with  the  origin  of  the 
antitoxins  in  the  bodies  of  immunised  animals,  the 
chemical  nature  of  these  substances,  or  the  mode  of 
their  action  in  neutralising  the  toxins.  These  are 
questions  which  would  involve  a  considerable  amount 
of  technical  knowledge  on  the  part  of  the  reader  for 


ANTITOXINS  85 

an  understanding  of  the  most  advanced  views  regard- 
ing them,  as  expounded  by  Ehrlich  and  others — Ehr- 
lich's  "side  chain  theory."  In  a  popular  treatise  a 
simple  statement  of  well  ascertained  facts  will,  I  hope, 
be  appreciated,  while  an  exposition  of  theories  still 
under  discussion  might  prove  wearisome. 

It  has  been  shown  that  the  antitoxins  when  mixed 
with  toxins  in  a  test-tube  exhibit  their  specific  neutral- 
ising action  as  shown  by  the  innocuousness  of  the 
mixture  when  injected  beneath  the  skin  of  a  sus- 
ceptible animal. 

The  antitoxin  of  snake  poison,  which  has  been  suc- 
cessfully used  in  India  for  the  cure  of  persons  bitten 
by  the  deadly  cobra,  when  mixed  with  cobra  venom 
in  proper  proportion  completely  neutralises  the  poi- 
sonous properties  of  this  venom.  Such  a  mixture 
injected  beneath  the  skin  of  a  small  animal  is  without 
effect.  But  if  the  mixture  is  heated  to  70°  C.  the 
antitoxin  is  destroyed  and  by  inoculation  experiments 
the  toxin  is  found  to  be  still  present  and  active. 

The  facts  stated  show  that  in  certain  infectious 
diseases  acquired  immunity  depends  upon  the  forma- 
tion of  antitoxins  in  the  bodies  of  immune  animals. 
But  these  antitoxins  have  no  power  to  destroy 
specific  disease  germs.  They  neutralise  the  toxic 
products  of  these  germs  without  exhibiting  any 
germicidal  action  upon  the  germs  themselves.  As, 


86  INFECTION  AND  IMMUNITY 

however,  the  power  of  the  germs  to  overcome  the 
resources  of  nature  and  invade  the  blood  or  tissues 
depends  upon  the  toxic  products  developed  by  them, 
they  are  deprived  of  their  power  to  multiply  in  the 
bodies  of  living  animals  when  these  poisonous  sub- 
stances are  neutralised.  Practically  they  become  as 
harmless  as  the  common  "saprophytic  bacteria"  which 
surround  us  on  all  sides,  and  are  swallowed  in  count- 
less numbers  with  every  glass  of  unsterilised  water 
we  drink. 

But  there  is  another  class  of  substances,  developed 
during  certain  diseases,  which  exhibit  specific  germi- 
cidal  activity  and  have  no  antitoxic  value.  Such  sub- 
stances are  found  in  the  blood  of  animals  which  have 
been  made  immune  to  the  pathogenic  action  of  the 
cholera  spirillum,  the  typhoid  bacillus,  and  the  bacillus 
of  hog  cholera. 

The  writer,  some  ten  years  ago,  obtained  experi- 
mental evidence  which  indicates  that  smallpox  im- 
munity probably  depends  upon  a  substance  which 
destroys  the  smallpox  germ,  rather  than  upon  an 
antitoxin. 

Further  details  with  reference  to  the  antitoxins 
will  be  found  in  Part  Second  of  this  volume,  in  which 
questions  relating  to  infection,  disinfection,  and  im- 
munity will  be  discussed  in  connection  with  the  more 
important  infectious  diseases,  considered  separately. 


PART  SECOND 
SPECIFIC  INFECTIOUS  DISEASES 


87 


CHAPTER  I 

BUBONIC  PLAGUE 

T^HE  history  of  bubonic  plague  extends  back  to 
a  remote  antiquity.  Greek  physicians  of  the 
second  and  third  century  before  the  Christian  era 
have  left  a  record  of  a  pestilential  malady  character- 
ised by  the  formation  of  buboes,  which  prevailed  in 
Libya,  in  Egypt,  and  in  Syria ;  and  two  Alexandrian 
physicians,  Dioscorides  and  Poseidonios,  who  were 
contemporaries  of  Christ,  have  given  a  description  of 
the  disease  which  leaves  no  doubt  as  to  its  identity 
with  the  plague  of  more  recent  times.  It  may  be 
well  to  explain  at  this  point  that  the  buboes  charac- 
teristic of  the  disease  are  enlarged  and  inflamed 
glands  in  the  groins,  in  the  armpits,  and  elsewhere, 
which  in  chronic  cases  may  suppurate  and  discharge 
a  virulent  pus  by  which  the  disease  is  propagated. 
We  now  know  that  the  germ  of  the  disease  is  found 
not  only  in  these  suppurating  buboes  but  also  in  the 
blood  of  an  infected  individual. 


90  INFECTION  AND  IMMUNITY 

Three  forms  of  the  disease  are  recognised  by 
modern  authors — one  a  mild  or  abortive  form,  in 
which  there  is  little  pain  or  fever  and  in  which  the 
buboes  rarely  suppurate.  In  this  form  the  enlarged 
glands  in  the  groin,  armpit,  and  neck  usually  disap- 
pear in  about  two  weeks.  In  its  usual  form  the 
disease  is  ushered  in  with  chilly  sensations,  fever, 
lassitude,  and  pain  in  the  back  and  limbs.  The  bu- 
boes are  quickly  developed  and  the  general  symp- 
toms soon  assume  a  grave  character.  If  the  patient 
lives  for  a  week  or  more,  the  buboes  usually  sup- 
purate and  carbuncles  and  boils  are  often  developed. 
In  the  third  or  fulminant  form  of  the  disease,  death 
may  occur  within  a  few  hours  from  the  outset  of  the 
attack  and  in  advance  of  the  development  of  the 
characteristic  buboes.  These  cases  could  scarcely  be 
recognised  were  it  not  for  the  fact  they  occur  during 
the  epidemic  prevalence  of  the  disease  among  per- 
sons who  have  been  exposed  to  infection. 

From  the  first  to  the  sixth  centuries  of  the  Christian 
era  we  have  no  authentic  accounts  of  the  prevalence 
of  bubonic  plague,  but  there  is  no  reason  to  believe 
that  it  had  entirely  disappeared  from  those  countries 
in  which  it  had  previously  prevailed.  During  the 
sixth  century,  however,  its  ravages  were  greatly  ex- 
tended and  it  prevailed  as  a  devastating  epidemic  in 
many  parts  of  the  Roman  Empire,  both  of  the  East 


BUBONIC  PLAGUE  91 

and  of  the  West;  indeed,  in  the  time  of  Justinian  it 
extended  far  beyond  the  limits  of  the  Roman  Em- 
pire. The  origin  of  this  extensive  epidemic  which 
raged  for  more  than  half  a  century  appears  to  have 
been  in  Lower  Egypt  in  the  year  542  ;  thence  it  ex- 
tended in  one  direction  along  the  north  coast  of 
Africa,  and  in  the  other  into  Palestine  and  Syria. 
The  following  year  it  invaded  Europe,  which  at  the 
time  was  in  a  state  of  political  disturbance  and  war- 
fare, and  during  this  and  subsequent  years  it  de- 
vastated many  sections  of  the  country,  depopulating 
towns  and  leaving  the  country  in  some  instances 
nothing  more  than  a  desert  inhabited  by  wild  beasts. 
The  accounts  given  of  this  widespread  epidemic  in- 
dicate that  other  infectious  maladies,  which  at  the  time 
had  not  been  clearly  recognised  as  specific  diseases, 
were  associated  with  the  plague  and  contributed  to 
the  general  mortality. 

During  the  middle  ages  epidemics  continued  to 
occur,  but  the  accounts  of  the  nature  of  the  prevail- 
ing "  pest "  are  usually  confused  and  unsatisfactory, 
and  it  was  not  until  nearly  the  middle  of  the  four- 
teenth century  that  the  horrible  epidemic  known  as 
the  black  death  devastated  Europe  and  caused  the 
death  of  more  than  25,000,000  of  its  inhabitants. 
There  has  been  considerable  difference  of  opinion 
among  the  best  authorities  as  to  whether  the  black 


92  INFECTION  AND  IMMUNITY 

death  of  the  fourteenth  century  was  identical  with 
bubonic  plague.  It  presented  some  features  which 
seem  to  distinguish  it  from  subsequent  epidemics, 
and  it  had  its  origin  from  a  different  quarter  of  the 
globe.  While  bubonic  plague  has  usually  invaded 
Europe  from  Egypt,  the  black  death  is  believed  to 
have  originated  in  Northern  China.  It  is  not  known 
exactly  when  or  where  this  epidemic  had  its  origin, 
but  it  is  known  to  have  reached  the  Crimea  in  1346 
and  Constantinople  the  following  year.  The  same 
year  it  was  conveyed  by  ships  to  several  seaports  of 
Italy  both  on  the  Mediterranean  and  the  Adriatic, 
and  also  to  Marseilles  on  the  French  coast;  in  1348 
it  extended  to  the  interior  of  these  countries  and  to 
Spain  ;  also  to  England,  Holland,  and  the  Scandi- 
navian peninsula.  The  following  year  it  completed 
the  invasion  of  Europe. 

The  disease  first  appeared  in  London  in  Novem- 
ber, 1348,  and  it  continued  to  prevail  in  various  parts 
of  England  for  a  period  of  eight  or  nine  years.  In 
1352  the  epidemic  prevailed  in  the  town  of  Oxford 
to  such  an  extent  that  this  town  lost  two-thirds  of 
its  academic  population.  The  plague  again  invaded 
England  in  1361  and  1368.  As  a  result  of  these 
devastating  epidemics  in  England,  as  well  as  in 
other  parts  of  Europe,  large  parts  of  the  country 
remained  for  a  time  uncultivated,  and  owing  to 


BUBONIC  PLAGUE  93 

the  lack  of  labourers  there  was  a  great  increase  in 
wages. 

The  following  graphic  account  of  the  ravages  of 
this  pestilence  is  by  a  writer  of  the  period  : 

"Wild  places  were  sought  for  sheiter;  some  went  into  ships 
and  anchored  themselves  far  off  on  the  waters.  But  the  angel 
that  was  pouring  the  vial  had  a  foot  on  the  sea  as  well  as  on  the 
dry  land.  No  place  was  so  wild  that  the  plague  did  not  visit  — 
none  so  secret  that  the  quick-sighted  pestilence  did  not  discover 
— none  could  fly  that  it  did  not  overtake.  For  a  time  all  com- 
merce was  in  coffins  and  shrouds,  but  even  that  ended.  Shrift 
there  was  none;  churches  and  chapels  were  open,  but  neither 
priests  nor  penitents  entered — all  went  to  the  charnel-house. 
The  sexton  and  the  physician  were  cast  into  the  same  deep  and 
wide  grave;  the  testator  and  his  heirs  and  executors  were  hurled 
from  the  same  cart  to  the  same  hole  together.  Fire  became  ex- 
tinguished, as  if  its  element  had  expired,  and  the  seams  of  the 
sailorless  ships  yawned  to  the  sun.  Though  doors  were  open 
and  coffers  unwatched,  there  was  no  theft;  all  offences  ceased,  and 
no  cry  but  the  universal  woe  of  the  pestilence  was  heard  among 
men." 

That  the  "  black  death"  of  the  fourteenth  century 
was  in  fact  the  same  disease  which  subsequently  pre- 
vailed in  Europe  under  the  name  of  "  the  plague," 
and  more  recently  known  as  "  bubonic  plague,"  can 
scarcely  be  doubted.  But  the  epidemic  was  character- 
ised by  an  unusually  large  number  of  cases  of  the 
pulmonary  form  of  the  disease,  in  which  it  seems 
probable  that  the  lungs  are  the  primary  seat  of  infec- 
tion, while  in  the  bubonic  form  the  bacillus  effects  a 


94  INFECTION  AND  IMMUNITY 

lodgment  through  some  superficial  wound  or  abra- 
sion, or  possibly  through  the  bites  of  insects,  and  it 
first  invades  the  lymphatics,  producing  inflammation 
of  the  nearest  lymphatic  glands.  General  invasion 
of  the  blood  appears,  from  recent  investigations,  to 
be  a  secondary  phenomenon  which  only  occurs  in 
very  severe  and  usually  fatal  cases. 

The  pulmonic  form  of  the  disease,  which  was  so 
prominent  in  the  epidemic  known  as  black  death,  is 
extremely  fatal  and  is  known  to  occur  at  the  present 
day. 

Bubonic  plague  continued  to  prevail  in  various  parts 
of  Europe  at  the  end  of  the  sixteenth  century,  and 
early  in  the  seventeenth  century  (1603)  an  epidemic 
occurred  in  London  which  caused  the  death  of  38,000 
of  its  inhabitants.  It  continued  to  prevail  in  this  city 
and  in  various  parts  of  England,  Holland,  and  Ger- 
many, and  six  years  later  caused  a  mortality  of  1 1,785 
in  the  city  of  London.  During  the  year  1603  a  most 
disastrous  epidemic  occurred  in  Egypt,  which  is  said 
to  have  caused  a  mortality  of  at  least  a  million.  After 
an  interval  of  ten  or  fifteen  years,  during  which  there 
was  a  marked  diminution  in  the  number  of  cases  and 
the  extent  of  its  distribution  in  European  countries, 
it  again  obtained  wide  prevalence  during  the  year 
1620  and  subsequently,  especially  in  Germany,  Hol- 
land, and  England.  The  epidemic  in  the  city  of 


B  U BO  NIC  PLA  GUE  95 

London  in  1625  caused  a  mortality  of  more  than 
35,000.  In  1630  a  severe  epidemic  occurred  in 
Milan,  and  in  1636  London  again  suffered  a  mor- 
tality of  over  10,000,  while  the  disease  continued  to 
claim  numerous  victims  in  other  parts  of  England 
and  on  "the  continent."  Later  in  the  century  (1656) 
some  of  the  Italian  cities  suffered  devastating  epi- 
demics. The  mortality  in  the  city  of  Naples  was  in 
the  neighbourhood  of  300,000,  in  Genoa  60,000,  in 
Rome  14,000.  The  smaller  mortality  in  the  last- 
named  city  has  been  ascribed  to  the  sanitary  meas- 
ures instituted  by  Cardinal  Gastaldi.  Up  to  this 
time  prayers,  processionals,  the  firing  of  cannons, 
etc.,  had  been  the  chief  reliance  for  the  arrest  of  pesti- 
lence, with  what  success  is  shown  by  the  brief  his- 
torical review  thus  far  presented.  This  enlightened 
prelate  inaugurated  a  method  of  combating  the 
plague  and  other  infectious  maladies  which,  with  in- 
creasing knowledge  and  experience  in  the  use  of 
scientific  preventive  measures,  has  given  us  the  mas- 
tery of  these  pestilential  diseases,  and  has  been  the 
principal  factor  in  the  extinction  of  bubonic  plague 
from  the  civilised  countries  of  Europe. 

But  it  was  long  after  the  time  of  Cardinal  Gas- 
taldi before  sanitary  science  was  established  upon  a 
scientific  basis  and  had  acquired  the  confidence  of 
the  educated  classes.  Indeed  the  golden  age  of 


96  INFECTION  AND  IMMUNITY 

preventive  medicine  has  but  recently  had  its  dawn,  and 
sanitarians  at  the  present  day  often  encounter  great 
difficulty  in  convincing  legislators  and  the  public  gen- 
erally of  the  importance  of  the  measures  which  have 
been  proved  to  be  adequate,  when  properly  carried 
out,  for  the  prevention  of  this  and  other  infectious 
maladies. 

We  have  now  arrived  in  our  review  at  the  period 
of  the  "  great  plague  of  London."  For  some  years 
this  city  had  been  almost  if  not  entirely  free  from  the 
scourge,  but  in  the  spring  of  1665  it  again  appeared 
and  within  a  few  months  caused  a  mortality  of  68,596 
in  a  population  estimated  at  460,000.  This,  how- 
ever,  does  not  fairly  represent  the  percentage  of 
mortality  among  those  exposed,  for  a  large  pro- 
portion of  the  population  fled  from  the  city  to 
escape  infection. 

Upon  the  continent  the  disease  prevailed  exten- 
sively, especially  in  Austria,  Hungary,  and  Germany. 
The  epidemic  in  Vienna  in  1679  caused  a  mortality 
of  76,000.  In  1 68 1  the  city  of  Prague  lost  83,000  of 
its  inhabitants.  During  the  last  quarter  of  this  cen- 
tury the  disease  disappeared  from  some  of  the  prin- 
cipal countries  of  Europe.  According  to  Hirsch,  it 
disappeared  from  England  in  1679,  from  France  in 
1668,  from  Holland  about  the  same  time,  from  Ger- 
many in  1683,  and  from  Spain  in  1681.  In  Italy  it 


B  U BON  1C  PL  A  GUE  97 

continued  to  prevail  to  some  extent  until  the  end  of 
the  century. 

At  the  beginning  of  the  eighteenth  century  bubonic 
plague  prevailed  in  Constantinople  and  at  various 
points  along  the  Danube ;  from  here  it  extended 
in  1704  to  Poland,  and  soon  after  to  Silesia,  Lithu- 
ania, Germany,  and  the  Scandinavian  countries.  The 
mortality  in  Stockholm  was  about  40,000.  The  dis- 
ease also  extended  westward  from  Constantinople 
through  Austria  and  Bohemia. 

In  1720  Marseilles  suffered  a  severe  epidemic, 
probably  as  a  result  of  the  introduction  of  cases  on  a 
ship  from  Leghorn.  The  mortality  was  estimated  as 
being  between  40,000  and  60,000.  From  Marseilles 
as  a  centre  it  spread  through  the  province  of  Provence, 
but  did  not  invade  other  parts  of  France.  In  1743  a 
severe  outbreak  occurred  on  the  island  of  Sicily.  A 
destructive  but  brief  epidemic,  which  is  estimated  to 
have  caused  a  mortality  of  300,000,  occurred  during 
the  years  1770  and  1771  in  Moldavia,  Wallachia, 
Transylvania,  Hungary,  and  Poland.  At  the  same 
time  the  disease  prevailed  in  Russia,  and  in  1771 
caused  the  death  of  about  one-fourth  of  the  popula- 
tion of  the  city  of  Moscow. 

Early  in  the  nineteenth  century  (1802)  bubonic 
plague  appeared  at  Constantinople  and  in  Armenia. 
It  had  previously  prevailed  in  the  Caucasus,  from 


98  INFECTION  AND  IMMUNITY 

which  province  it  extended  into  Russia.  In  1808  to 
1813  it  extended  from  Constantinople  to  Odessa,  to 
Smyrna,  and  to  various  localities  in  Transylvania.  It 
also  prevailed  about  the  same  time  in  Bosnia  and 
Dalmatia.  In  1812  to  1814  it  prevailed  in  Egypt, 
and,  as  usual,  was  conveyed  from  there  to  European 
countries.  During  the  same  year  it  prevailed  extens- 
ively in  Moldavia,  Wallachia,  and  Bessarabia.  In 
1831  it  again  prevailed  as  an  epidemic  in  Constanti- 
nople and  various  parts  of  Roumelia,  and  again  it 
appeared  in  Dalmatia  in  1840  and  in  Constantinople 
in  1841.  Egypt,  which  for  centuries  had  been  the 
principal  focus  from  which  plague  had  been  intro- 
duced into  Europe,  continued  to  suffer  from  the 
disease  until  1845,  when  it  disappeared  from  that 
country. 

The  last  appearance  of  Oriental  plague  in  Europe, 
until  its  recent  introduction  into  Portugal,  was  the 
outbreak  on  the  banks  of  the  Volga  in  1878-79. 
The  disease  had  previously  prevailed  in  a  mild  form 
in  the  vicinity  of  Astrakhan  and  was  probably  intro- 
duced from  that  locality.  An  interesting  fact  in  con- 
nection with  this  epidemic  is  that  in  Astrakhan  the 
disease  was  so  mild  that  no  deaths  occurred,  and  that 
the  earlier  cases  on  the  right  bank  of  the  Volga  were 
of  the  same  mild  form,  but  that  the  disease  there  in- 
creased rapidly  in  severity,  and  soon  became  so  ma- 


B  UBONIC  PLA  G  UE  99 

lignant  that  scarcely  any  of  those  attacked  recovered. 
This  is  to  some  extent  the  history  of  epidemics  else- 
where, and  not  only  of  plague,  but  of  other  infectious 
diseases,  such  as  typhus  fever,  cholera,  and  yellow- 
fever.  In  all  of  these  diseases  the  outset  of  an  epi- 
demic may  be  characterised  by  cases  so  mild  in  char- 
acter that  they  are  not  recognised,  and  during  the 
progress  of  the  epidemic  many  such  cases  may  con- 
tinue to  occur.  These  cases  are  evidently  especially 
dangerous  as  regards  the  propagation  of  the  disease, 
for  when  they  are  not  recognised  no  restrictions  are 
placed  upon  the  infected  individuals,  although  they 
may  be  sowing  the  germs  broadcast. 

The  termination  of  an  epidemic  in  the  pre-sanitary 
period  depended  to  a  considerable  extent  upon  the 
fact  that  those  who  suffered  a  mild  attack  acquired 
thereby  an  immunity,  and  that  when  the  more  sus- 
ceptible individuals  in  a  community  had  succumbed 
to  the  prevailing  disease  there  was  a  necessary  termi- 
nation of  the  epidemic  for  want  of  material. 

Another  factor  which,  no  doubt,  has  an  important 
bearing  upon  the  termination  of  epidemics  is  a  change 
in  the  virulence  of  the  germ  as  a  result  of  various 
natural  agencies.  Time  will  not  permit  me  to  dis- 
cuss this  subject  in  its  scientific  and  practical  aspects, 
but  the  general  fact  may  be  stated  that  all  known 
disease  germs  may  vary  greatly  in  their  pathogenic 


ioo  INFECTION  AND  IMMUNITY 

virulence,  and  that  in  every  infectious  disease  mild 
cases  may  occur,  not  only  because  of  the  slight  sus- 
ceptibility of  the  individual,  but  also  because  of  the 
"attenuated"  virulence  of  the  specific  germ.  In  the 
eighteenth  century,  the  beginning  of  sanitary  science, 
isolation  of  the  sick,  and  seaboard  quarantines  came 
to  the  aid  of  these  natural  agencies,  and  did  much  in 
the  way  of  arresting  the  progress  of  this  pestilential 
disease.  At  the  present  day  these  measures,  together 
with  disinfection  by  heat  or  chemical  agents,  are 
relied  upon  by  sanitarians  with  great  confidence  as 
being  entirely  adequate  for  the  exclusion  of  this 
disease  or  for  stamping  it  out  if  it  should  effect  a 
lodgment  in  localities  where  an  enlightened  public 
sentiment  permits  the  thorough  execution  of  these 
preventive  measures;  but  when  the  disease  prevails 
among  an  ignorant  population  which  strenuously  ob- 
jects to  the  carrying  out  of  these  measures,  the  con- 
test between  the  sanitary  officer  and  the  deadly  germ 
is  an  unequal  one,  and  the  stamping  out  of  an  epi- 
demic becomes  a  task  of  great  magnitude,  if  not 
entirely  hopeless.  This  is  illustrated  by  the  experi- 
ence of  the  English  in  their  encounter  with  bubonic 
plague  in  their  Indian  Empire. 

Plague  seemed  to  be  almost  a  thing  of  the  past 
and  no  longer  gave  any  uneasiness  in  the  countries 
of  Europe  which  had  formerly  suffered  from  its  rav- 


B U BON  1C  PLA GUE  i o i 

ages,  when  in  February,  1894,  it  made  its  appearance 
in  the  city  of  Canton,  China,  and  three  months  later 
in  Hong  Kong.  The  disease  is  known  to  have 
been  epidemic  in  the  province  of  Yunnan,  which 
is  about  nine  hundred  miles  distant  from  Canton, 
since  the  year  1873,  but  it  attracted  little  atten- 


FIG.  i.     Bacillus  of  bubonic  plague.      A,  magnified  rooo  diameters  ;      B, 
more  highly  magnified  to  show  li  end-staining." 

tion  until  the  lives  of  Europeans  living  in  the  city 
of  Hong  Kong  were  threatened  by  the  outbreak  of 
an  epidemic  among  the  Chinese  residents  of  that 
place.  Many  thousands  of  deaths  occurred  in  Can- 
ton during  the  three  months  which  elapsed  after  its 
introduction  to  that  city  before  it  effected  a  lodgment 
in  Hong  Kong. 

Fortunately  this  outbreak   gave  the    opportunity 


102  INFECTION  AND  IMMUNITY 

for  competent  bacteriologists  to  make  scientific  in- 
vestigations relating  to  the  specific  cause  of  this 
scourge  of  the  human  race  and  to  the  demonstration 
that  it  is  due  to  a  minute  bacillus.  This  discovery 
was  first  made  by  the  Japanese  bacteriologist,  Kita- 
sato,  who  had  received  his  training  in  the  laboratory 
of  the  famous  Professor  Robert  Koch,  of  Berlin. 
This  discovery  was  made  in  the  month  of  June,  1894, 
in  one  of  the  hospitals  established  by  the  English 
officials  in  Hong  Kong.  About  the  same  time  the 
discovery  was  made,  independently,  by  the  French 
bacteriologist,  Yersin.  From  this  time  the  study  of 
the  plague  has  been  established  upon  a  scientific 
basis  and  very  material  additions  have  been  made  to 
our  knowledge  with  reference  to  the  prevention  and 
treatment  of  the  disease. 

That  the  plague  bacillus  has  not  lost  any  of  its 
original  virulence  is  amply  demonstrated  by  the  high 
death-rate  among  those  attacked,  and  we  are  justified 
in  ascribing  its  restricted  prevalence  to  the  general 
improvement  in  sanitary  conditions  in  civilised  coun- 
tries and  to  the  well  directed  efforts  of  public  health 
officers  in  the  various  localities  to  which  it  has  been 
introduced  during  recent  years.  In  the  Philippine 
Islands,  where  it  prevailed  to  a  considerable  extent 
when  our  troops  first  took  possession  of  the  city  of 
Manila  and  where  the  conditions  among  the  natives 


BUBONIC  PLAGUE  103 

are  extremely  favourable  for  its  extension,  it  has  been 
kept  within  reasonable  bounds  and,  indeed,  the  latest 
reports  indicate  that  it  has  been  practically  extermin- 
ated by  the  persistent  efforts  of  the  medical  officers 
of  our  army,  charged  with  the  duty  of  protecting  the 
public  health  in  those  islands. 

The  monthly  report  of  the  Board  of  Health  for 
the  city  of  Manila  for  September,  1902,  the  last  at 
hand,  records  but  one  death  from  plague  during  that 
month.  During  the  same  period  there  were  ten 
deaths  from  typhoid  fever,  thirty-five  deaths  from 
dysentery,  and  seventy-six  deaths  from  "  the  great 
white  plague,"  pulmonary  tuberculosis. 

Bubonic  plague,  cholera,  and  typhoid  fever  have 
long  been  classed  as  "  filth-diseases,"  and  in  a  certain 
sense  this  is  correct,  although  we  now  know  that  the 
germs  of  these  diseases  not  only  are  not  generated 
by  filth,  but  do  not  multiply  in  accumulations  of  filth. 
They  are'  present,  however,  in  the  alvine  discharges 
of  the  sick,  and  when  this  kind  of  filth  is  exposed 
in  the  vicinity  of  human  habitations  or  gains  access 
to  wells  or  streams,  the  water  of  which  is  used  for 
drinking,  the  germs  are  likely  to  be  conveyed  to  the 
alimentary  canals  of  susceptible  individuals,  and  thus 
the  disease  is  propagated.  Until  quite  recently  the 
attention  of  sanitarians  was  so  firmly  fixed  upon  the 
demonstrated  transmission  of  cholera  and  typhoid 


104  INFECTION  AND  IMMUNITY 

fever  through  the  agency  of  contaminated  water  or 
milk  that  certain  other  modes  of  transmission  were 
overlooked,  or  at  least  underrated.  I  refer  to  the 
transmission  by  insects,  or  as  dust  by  currents  of  air. 
I  have  for  many  years  insisted  upon  the  part  played 
by  flies  as  carriers  of  infectious  material  from  moist 
masses  of  excreta  from  cases  of  cholera  and  typhoid 
fever.  There  is  good  reason  to  believe  that  the 
bacillus  of  bubonic  plague  may  be  transmitted  in  the 
same  way. 

Certain  of  the  lower  animals,  including  rats  and 
mice,  are  very  susceptible  to  infection,  and  they  play 
an  important  part  in  the  propagation  of  the  disease. 
The  germs  are  found  not  only  in  the  blood  and  in 
pus  from  suppurating  buboes,  but  also  in  the  dis- 
charges from  the  bowels  of  the  sick  and  of  infected 
rats.  This  being  the  case  it  can  readily  be  seen  how 
important  a  strict  sanitary  police  is  in  arresting  the 
spread  of  an  epidemic. 

Dr.  James  A.  Lowson,  who  has  written  an  excel- 
lent account  of  the  epidemic  in  Hong  Kong,  says  : 

"  Filth  and  overcrowding  must  be  recorded  as  two  of  the 
most  important  factors.  The  district  of  Torpingshan  supplied 
these  factors  in  a  marked  degree  at  the  beginning  of  the  out- 
break, the  majority  of  the  houses  being  in  a  most  filthy  con- 
dition, as,  owing  to  the  uncleanly  habits  of  the  people,  the 
amount  of  what  is  generally  termed  rubbish  accumulates  in  a 
Chinese  house  in  a  crowded  city  to  an  extent  beyond  the  imagi- 


BUBONIC  PLAGUE  105 

nation  of  civilised  people.  When  to  a  mixture  of  dust,  old 
rags,  ashes,  broken  crockery,  moist  surface  soil,  etc.,  are  added 
fecal  matter  and  the  decomposing  urine  of  animals  and  human 
beings,  a  terribly  insanitary  condition  of  affairs  prevails." 

The  period  of  incubation  in  bubonic  plague — the 
time  which  elapses  between  exposure  to  infection  and 
the  development  of  the  disease — is  usually  from  three 
to  six  days. 

From  the  report  of  Dr.  Lowson  of  cases  treated  in 
the  various  hospitals  of  Hong  Kong,  under  the  con- 
trol of  English  physicians,  it  appears  that  the  mortal- 
ity was  much  greater  among  natives  of  Hong  Kong 
than  among  the  foreign  residents  of  that  city.  The 
mortality  among  Europeans  (i  i  cases  only)  was  13.2$; 
among  Japanese  (10  cases),  60  % ;  among  Portuguese 
(18  cases),  66$;  among  Chinese  (2619  cases),  93.4$. 
To  a  considerable  extent,  no  doubt,  this  difference  in 
mortality  was  due  to  the  unfavourable  surroundings 
of  the  natives  and  their  lack  of  proper  nursing  and 
medical  attendance,  many  of  them  being  brought  to 
the  hospital  in  a  dying  condition. 

Experiments  upon  rats  and  other  animals  show 
that  they  become  infected  when  cultures  of  the 
plague-bacillus  are  deposited  upon  the  mucous  mem- 
brane of  the  nose. 

During  the  epidemic  prevalence  of  the  disease 
these  animals  die  in  large  numbers,  and  there  is  good 


io6  INFECTION  AND  IMMUNITY 

reason  to  believe  that  they  play  an  important  part 
in  the  propagation  of  the  malady.  It  has  been  sug- 
gested that  infection  may  be  carried  from  rats  to  man 
through  the  agency  of  fleas  which  swarm  upon  these 
rodents  and  desert  them  when  they  die. 

The  Japanese  physician,  Aoyoma,  who  was  associ- 
ated with  Kitasato,  and  who  contracted  the  disease 
but  recovered,  is  of  the  opinion  that  in  a  great  major- 
ity of  the  cases,  and  perhaps  in  all,  infection  occurs 
through  an  external  wound.  He  calls  attention  to 
the  fact  that  physicians  and  nurses  in  attendance 
upon  cases  of  the  disease  rarely  become  infected,  and 
states  that  during  the  epidemic  of  1894  in  Hong  Kong 
only  three  Japanese  and  one  Chinese  physician  be- 
came infected,  while  all  of  the  nurses  escaped  ;  also  to 
the  fact  that  of  three  hundred  English  soldiers  who 
volunteered  to  clean  and  disinfect  the  Chinese  pest- 
houses  during  the  prevalence  of  the  epidemic,  only 
ten  contracted  the  disease.  The  greater  liability  of 
the  lower  class  of  natives  to  contract  the  disease,  he 
ascribes  not  only  to  the  insanitary  surroundings  in 
which  they  live,  but  also  to  the  fact  that  they  seldom 
wear  shoes  and  stockings,  and  thus  are  very  liable  to 
infection  through  insignificant  wounds,  scratches,  or 
abrasions,  both  of  the  feet  and  hands.  In  this  con- 
nection it  is  well  to  call  attention  to  the  fact  that  in 
former  epidemics  physicians  have  suffered  severely, 


BUBONIC  PLAGUE  107 

and  that  whatever  immunity  they  enjoy  is  due  to  the 
observance  of  sanitary  precautions,  the  importance  of 
which  has  become  apparent  as  we  have  acquired  a 
more  exact  knowledge  of  the  etiology  of  the  disease. 

During  the  past  few  years  a  number  of  prominent 
bacteriologists  have  been  engaged  in  researches  re- 
lating to  the  prevention  and  cure  of  bubonic  plague 
by  means  of  an  antitoxic  serum,  obtained  by  the  same 
method  and  in  accordance  with  the  same  funda- 
mental scientific  principle  as  in  the  case  of  the  anti- 
toxic serum  which  is  now  so  successfully  employed  in 
the  treatment  of  diphtheria.  The  experiments  thus  far 
made  have  apparently  been  attended  with  a  consider- 
able degree  of  success.  Professor  Calmette  reports 
that  the  serum  of  Yersin  prepared  at  the  Pasteur 
Institute  in  Paris  proved  to  be  curative  in  a  con- 
siderable proportion  of  the  cases  treated  during  the 
recent  outbreak  at  Oporto,  and  that  protective  inocu- 
lation conferred  a  temporary  immunity,  which,  how- 
ever, did  not  last  longer  than  twenty  days.  The 
mortality  in  cases  not  treated  by  Yersin's  serum  was 
70  %,  in  those  treated  with  it  13  %. 

The  inoculations  made  by  Haffkine  in  Bombay 
appear  to  have  been  quite  successful.  In  his  first 
experiment  8142  persons  were  inoculated.  Of  these, 
1 8  subsequently  contracted  the  disease  and  2  died. 
Among  4926  persons  inoculated  a  single  time  at 


io8  INFECTION  AND  IMMUNITY 

Dharwan  45  were  subsequently  attacked  and  15 
died  ;  while  among  3387  persons  in  whom  a  second 
inoculation  was  made,  only  2  were  attacked.  Haff- 
kine  uses  in  his  inoculations  a  sterilised  culture  of 
the  plague-bacillus.  The  inoculation  is  followed  by 
slight  fever  and  enlargement  of  the  nearest  lymphatic 
glands.  All  symptoms  disappear  at  the  end  of  two 
or  three  days. 

The  plague-bacillus  is  very  easily  destroyed  by 
disinfectants.  Dr.  Lowson  reports  that  a  i  %  solu- 
tion of  carbolic  acid  kills  the  bacilli  within  an  hour, 
a  2  %  solution  almost  immediately.  Quicklime  was 
almost  as  prompt  in  its  action.  Exposure  to  fresh  air 
for  three  or  four  days  usually  destroys  the  vitality  of 
the  bacillus,  and  exposure  to  direct  sunlight  destroys 
it  in  three  or  four  hours.  Kitasato  and  Yersin  both 
arrived  at  the  conclusion  that  the  disease  may  be 
contracted  by  inoculation,  through  a  wound  or  abra- 
sion ;  by  way  of  the  respiratory  tract  when  the  bacillus 
is  present  in  dust  carried  by  the  inspired  air ;  or  by 
way  of  the  stomach  when  food  or  drink  taken  con- 
tains the  bacillus. 

What  has  been  said  indicates  very  clearly  the 
proper  preventive  measures,  and  when  these  are  en- 
forced with  energy  and  intelligence  there  need  be 
little  fear  of  the  epidemic  extension  of  the  disease. 

For  the  prevention  of  this  and  other  filth  diseases, 


BUBONIC  PLAGUE  109 

our  main  reliance  must  rest  upon  isolation  of  the 
sick,  disinfection  of  all  infectious  material,  and  gen- 
eral sanitary  police  of  infected  localities.  The  de- 
struction of  rats  in  localities  infected,  or  likely  to 
become  so,  is  also  a  measure  of  prime  importance. 
Protective  inoculations  will  hardly  be  necessary  if 
the  measures  above  referred  to  are  vigorously  en- 
forced, and  in  the  opinion  of  the  writer  it  is  only 
under  exceptional  circumstances  that  such  inocula- 
tions need  be  practised  on  a  large  scale.  Those 
whose  duties  require  them  to  care  for  the  sick  or  visit 
infected  localities  may  be  given  such  protection  as 
is  afforded  by  Haffkine's  inoculations.  But  the  im- 
munisation of  entire  communities  by  inoculation  in 
anticipation  of  a  possible  plague  epidemic  hardly 
seems  necessary  in  the  present  state  of  sanitary 
knowledge. 


CHAPTER  II 

ASIATIC  CHOLERA 

A  SI  AT  1C  cholera  has  its  permanent  home  in  In- 
*~*  dia,  and  especially  in  the  thickly  populated  region 
occupied  by  the  delta  of  the  Ganges,  the  principal 
city  of  which  is  Calcutta.  Here  it  prevails  through- 
out the  year,  with  a  period  of  maximum  intensity 
in  the  hot  and  comparatively  dry  month  of  April. 
Heavy  rains  have  a  salutary  sanitary  influence  in  this 
and  other  regions  where  the  disease  is  prevalent. 
From  the  infected  area  referred  to,  the  disease 
spreads  almost  annually  to  other  parts  of  India  and 
neighbouring  Asiatic  countries,  and  at  intervals  has 
extended  its  ravages  to  Africa,  Europe,  and  America. 
These  widespread  epidemics  are,  however,  of  com- 
paratively recent  origin. 

After  a  devastating  epidemic  in  India  during  the 
years  1816  to  1819  the  disease  extended  to  Mauritius 
and  the  east  coast  of  Africa,  to  Farther  India  and  the 
islands  of  Sumatra,  Java,  and  Borneo,  and  to  China. 


no 


ASIATIC  CHOLERA  in 

Two  or  three  years  later  the  disease  prevailed  in 
Syria  and  Palestine,  and  for  the  first  time,  so  far 
as  is  known,  appeared  in  a  European  country,  in 
Astrakan.  A  second  great  epidemic,  beginning  in 
India  in  1826,  reached  Astrakan  in  1830.  Thence  it 
extended  as  far  north  as  St.  Petersburg.  The  fol- 
lowing spring  it  invaded  Poland  and  extended  from 
Austria  into  Germany.  At  the  same  time  it  had 
been  carried  by  way  of  Persia,  Mesopotamia,  Arabia, 
and  Palestine  into  Egypt.  Hungary,  Austria,  and 
Turkey  were  invaded  during  the  same  year  (1831), 
and  it  finally  reached  Great  Britain,  where  in  1832  it 
obtained  wide  prevalence.  In  this  year  also  France, 
Belgium,  and  Holland  were  invaded. 

In  1832  it  reached  the  United  States  by  way  of 
Canada,  where  it  was  carried  by  Irish  immigrants. 
It  spread  rapidly  along  the  St.  Lawrence  and  the 
shores  of  Lake  Ontario.  By  an  independent  import- 
ation it  was  brought  in  the  same  year  to  New  York 
and  spread  thence  southward  and  westward,  invading 
the  States  of  Pennsylvania,  Virginia,  Maryland,  Ken- 
tucky, Ohio,  Indiana,  and  Illinois,  and  in  October 
first  appeared  in  the  city  of  New  Orleans.  The  fol- 
lowing summer  it  broke  out  afresh  in  this  city  and 
rapidly  spread  through  the  southern,  central,  and 
western  States.  It  also  invaded  the  Indian  Territory 
and  California.  In  1834  it  reappeared  in  the  eastern 


1 1 2  INFECTION  AND  IMMUNITY 

States,  and  in  1835  was  reintrodueed  from  Cuba  to 
the  city  of  New  Orleans.  In  the  meantime  Mexico 
had  been  invaded,  and  subsequently  the  disease  ob- 
tained a  limited  prevalence  in  Central  America  and 
the  Gulf  coast  of  South  America.  Simultaneously 
with  this  widespread  epidemic  in  America  the  disease 
spread  in  Europe  to  Sweden  and  Norway  in  the 
north  and  to  Italy,  Spain,  and  Portugal  in  the  south. 
The  disease  died  out  during  the  winter  of  1837-38, 
and  for  the  ten  following  years  Europe,  Africa,  and 
America  remained  free  from  this  scourge  of  the 
human  race.  In  1846  the  disease,  which  had  pre- 
viously shown  increased  epidemic  extension  in  India, 
obtained  ^wide  prevalence  in  Persia,  thence  it  ex- 
tended to  Arabia,  and  the  following  year  reached 
Constantinople.  In  1848  it  spread  through  Turkey, 
Hungary,  Asia  Minor,  Syria,  and  Egypt. 

In  the  meantime  it  had  been  introduced  into  Russia 
(in  1847),  and  early  in  the  summer  of  1848  reached 
Germany.  In  the  autumn  of  this  year  it  was  intro- 
duced into  England  and  Scotland,  and  the  following 
year  obtained  wide  prevalence  in  the  British  Isles. 
Holland  and  Belgium  were  invaded  at  the  same  time, 
and  in  1849  France  and  Austria  suffered  severe  epi- 
demics. Northern  Italy  also  suffered  from  the  disease, 
which  indeed  prevailed  in  all  parts  of  Europe,  with 
the  exception  of  Spain  and  Portugal,  which  countries 


ASIA  TIC  CHOLERA  1 13 

remained  exempt.  In  December,  1848,  cholera  was 
brought  from  Europe,  by  emigrant  ships,  both  to 
New  York  and  to  New  Orleans.  From  the  last- 
named  city  it  spread  northward  to  Memphis  and 
westward  into  the  State  of  Texas,  and  during  the 
year  1849  nearly  all  of  the  States  east  of  the  Rocky 
Mountains  suffered  to  a  greater  or  less  extent,  es- 
pecially those  located  in  the  valleys  of  the  Ohio  and 
Mississippi  rivers.  It  continued  to  prevail  during 
the  following  year  (1850),  and  in  October  was  car- 
ried to  San  Francisco  by  way  of  the  Isthmus  of  Pan- 
ama. During  this  epidemic  the  West  Indies  suffered 
severely,  especially  the  islands  of  Cuba  and  Jamaica. 
It  also  prevailed  in  Mexico,  and  to  some  extent  in 
South  America.  The  epidemic  did  not  terminate  in 
the  Western  Hemisphere  until  the  end  of  the  year 
1854,  but  in  Europe  it  had  practically  ceased  to  pre- 
vail, except  in  a  few  localities  in  northern  Europe, 
by  the  close  of  the  year  1850. 

In  the  spring  of  1852  another  widespread  epidemic 
was  inaugurated.  The  disease  appeared  almost  at 
the  same  time  in  Persia,  Mesopotamia,  and  Poland, 
apparently  as  a  survival  from  the  previous  epidemic, 
and  extended  to  adjacent  countries.  In  Russia  it 
continued  to  prevail  to  some  extent  during  a  period 
of  ten  years,  the  years  1853,  1855,  and  1859  being 
notable  as  marking  its  widest  extension  and  the 


ii4  INFECTION  AND  IMMUNITY 

greatest  mortality.  This  was  also  the  case  in  north- 
ern Germany.  In  1855,  Austria  and  Italy  suffered 
severely.  The  disease  was  brought  to  England  from 
Germany  in  1853  an<^  extended  to  various  parts 
of  the  island  during  this  and  the  following  year. 
France  also  suffered  severely  from  the  disease  at  this 
time  (1853-54),  and  also  Spain  and  Portugal,  where  it 
prevailed  during  the  period  from  1853  to  J86o.  In 
North  America  the  disease  was  introduced  into 
Canada  in  1853,  and  obtained  wide  extension  through- 
out the  United  States  in  1854.  The  disease  disap- 
peared from  the  countries  of  North  America  the 
following  year,  but  in  Central  America  and  in  South 
America  it  prevailed  to  some  extent  for  several  years 
subsequent  to  this  date,  although  the  year  1855  was 
that  of  greatest  extension  and  fatality. 

Another  epidemic  period  is  that  embraced  between 
the  years  1865  and  1875.  As  usual,  the  epidemic 
extension  of  the  disease  in  Europe  was  preceded  by 
a  period  of  increased  fatality  in  its  native  haunts,  in 
the  lower  basin  of  the  Ganges,  and  also  by  its  exten- 
sion to  other  eastern  countries  —  China,  Japan.  I 
shall  not  attempt  to  follow  the  progress  of  the  dis- 
ease through  the  countries  of  Europe,  but,  as  show- 
ing its  fatal  character,  will  give  some  mortality 
statistics.  The  epidemic  of  1867  in  Italy  was  at- 
tended by  a  mortality  of  130,000.  In  Prussia,  during 


ASIATIC  CHOLERA  115 

the  year  1866,  114,683  deaths  were  reported.  In 
England  the  disease,  in  1865  and  the  next  year, 
caused  a  mortality  of  14,378,  nearly  half  of  the  deaths 
occurring  in  the  city  of  London.  In  Belgium  a  mort- 
ality of  32,812  occurred  during  the  year  of  greatest 
prevalence  (1866). 

In  North  America  the  disease  was  introduced  in 
1866  by  three  independent  importations,  to  New 
York,  New  Orleans,  and  Halifax.  The  following 
year  it  obtained  wide  extension,  especially  in  the 
western  States  and  in  Texas. 

Again  cholera  invaded  Europe  during  1871-73, 
and  again  it  was  introduced  into  the  United  States 
by  way  of  New  Orleans,  and  thence  spread  to  some 
extent  in  the  valley  of  the  Mississippi,  and  along  its 
principal  tributaries.  The  epidemic  of  1872  is  esti- 
mated to  have  cost  120,000  lives  in  Russia,  and  the 
previous  year  the  mortality  was  still  greater.  In 
Hungary  the  disease  claimed  190,000  victims  during 
the  years  1872  and  1873.  In  Prussia  the  number  of 
deaths  in  1873  was  28,790. 

Cholera  disappeared  from  Europe  and  America  in 
1873,  and  the  next  great  epidemic  was  inaugurated 
in  1884,  when  it  reached  the  shores  of  France  and 
Italy.  According  to  Dr.  Shakespeare,1  this  epidemic 
"cost  France  15,000  of  its  inhabitants  in  1884,  J885, 

1  Report  on  Cholera  in  Europe  and  India,  by  E.  O.  Shakespeare,  M.D.  (1890). 


n6  INFECTION  AND  IMMUNITY 

and  1886;  Spain,  180,000  in  1884  and  1885  ;  Aus- 
tria-Hungary, 4000  inhabitants  in  1886;  Italy,  about 
50,000  inhabitants  in  1884,  1886,  and  1887." 

In  Japan,  the  epidemic  of  1885  was  attended  with 
a  mortality  of  109,434. 

In  1891  cholera  prevailed  extensively  in  India, 
Syria,  Arabia,  Siam,  and  Japan,  and  was  introduced 
into  Austria  by  way  of  Persia.  By  November,  1892, 
it  is  estimated  that  half  a  million  cases  had  occurred 
in  Russia  with  a  mortality  of  at  least  50  per  cent. 
A  severe  outbreak  of  the  disease  occurred  in  the  city 
of  Hamburg  during  the  month  of  August  of  this 
year,  resulting  in  8005  deaths.  From  Hamburg  the 
disease  was  brought  to  New  York  harbour  on  sev- 
eral ships  carrying  immigrants,  but  owing  to  the 
vigorous  measures  adopted  by  the  local  health  author- 
ities, assisted  by  the  Marine  Hospital  Service,  the 
disease  was  arrested  at  the  threshold  of  the  country 
and  an  epidemic  was  averted.  The  success  obtained 
at  this  time  shows  what  can  be  accomplished  by  sani- 
tary measures  based  upon  an  exact  knowledge  with 
reference  to  the  specific  cause  of  the  disease  (cholera 
germ)  and  its  mode  of  transmission.  The  extension 
of  cholera  from  its  home  in  India  to  the  countries  of 
Europe  and  America,  which  first  occurred  during  the 
nineteenth  century,  was  no  doubt  due  to  the  increased 
facilities  for  rapid  transit,  especially  by  steamboats 


ASIATIC  CHOLERA  117 

and  railroads.  Infected  individuals  leaving  the  lo- 
calities where  they  had  contracted  the  disease,  would 
fall  by  the  way,  or  recover  before  travelling  any  great 
distance,  if  restricted  to  the  methods  of  transportation 
available  before  the  introduction  of  steam  as  a  motive 
power  for  ships  and  railroad  coaches.  The  fact  that 
cholera  is  carried  from  place  to  place  by  men,  follow- 
ing routes  of  travel,  is  well  stated  by  the  German 
physician  Griesinger.  He  says  : 

"  Cholera  has  never  advanced  like  a  broad  stream  inundating 
entire  countries  at  one  time,  bringing  disease  to  all  regions  lying 
parallel  with  each  other,  over  a  wide  extent,  but  it  always  ad- 
vances in  relatively  narrow  lines  from  which  usually,  but  not 
always,  lateral  offshoots  arise.  In  countries  with  a  small  popu- 
lation we  see  constantly  that  this  district  corresponds  with  the 
great  lines  of  travel.  If  the  disease  oversteps  high  mountains, 
if  it  passes  through  a  desert,  if  it  crosses  the  ocean,  it  always  fol- 
lows the  lines  of  human  intercourse,  the  post  and  military  routes, 
the  caravan  and  sailing  routes,  etc.  If  it  has  broken  out  on  an 
island,  then  the  first  cases  have  always  been  in  a  seaport,  never  in 
the  interior." 

We  now  know  definitely  that  the  cholera  germ  is 
carried  from  place  to  place  by  cholera-infected  in- 
dividuals, who  harbour  this  deadly  spirillum  in  their 
intestines  and  leave  it  wherever  the  discharges  from 
their  bowels  are  deposited.  Mild  cases  of  "  choleraic 
diarrhoea"  are  even  more  dangerous  as  regards  the 
propagation  of  the  disease  than  severe  and  fatal  cases, 
for  the  infected  individual  may  not  suspect  the  nature 


u8  INFECTION  AND  IMMUNITY 

of  a  malady  which  he  considers  trivial,  and,  instead 
of  being  isolated  and  properly  treated  as  he  should 
be  in  his  own  interest  and  that  of  the  public  gener- 
ally, he  goes  from  town  to  town  or  from  country  to 
country  distributing  cholera  germs  by  the  way. 

Cholera  is  contracted  only  by  the  introduction  of 
cholera  germs  into  the  intestinal  canal  by  way  of  the 
mouth  and  stomach.  The  spirillum  is  easily  destroyed 
by  acids,  and  consequently  does  not  multiply  in  the 
healthy  human  stomach,  and,  under  ordinary  condi- 
tions, probably  does  not  survive  to  reach  the  intes- 
tine, owing  to  the  germicidal  action  of  the  acid  gastric 
juice.  But  any  derangement  of  the  digestive  process 
predisposes  to  an  attack  of  the  disease.  Excesses  in 
eating  or  drinking  cause  the  individual  to  be  more 
susceptible  to  infection.  In  Germany  it  has  been 
noted  that  an  increase  in  the  number  of  cases  is 
likely  to  occur  on  Sunday,  because  of  the  indulgence 
of  the  labouring  classes  in  wine  and  beer  during  this 
day  of  rest  and  recreation. 

Invalids,  and  especially  those  subject  to  disorders 
of  the  stomach  and  bowels,  are  especially  liable  to 
contract  the  disease  during  its  epidemic  prevalence. 
But  it  is  safe  to  say  that  no  one  will  contract  cholera 
unless  living  cholera  germs  are  introduced  into  the 
intestinal  canal.  This  usually  occurs  as  a  result  of 
drinking  cholera-infected  water,  or  partaking  of  food 


ASIATIC  CHOLERA 


119 


which  in  some  way  has  become  infected  and  which 
has  not  been  sterilised  by  heat.  The  cholera  spiril- 
lum is  so  easily  destroyed  by  heat  that  the  prevention 
of  the  disease  is  a  comparatively  simple  matter.  Any 
article  of  food  or  drink  which  has  been  subjected  for 
a  few  minutes  to  a  temperature  of  140°  Fahr.  (60° 
C.)  is  absolutely  safe,  unless  it  has  been  reinfected 
after  such  exposure.  Such  reinfection  might  occur  if 
the  sterilised  food  or  liquid  is  exposed  to  contamina- 
tion by  infected  flies.  These  insects,  without  doubt, 
not  infrequently  act  as  carriers  of  infection  from  ex- 
posed cholera  excreta — on  the  ground  or  in  shallow 
pits — to  articles  of  food  or  drink  which  they  light 
upon  or  fall  into.  When  the  water  supply  of  a  town 
becomes  infected  as  a  result  of  contamination  by 
cholera  excreta,  a  general  epidemic  is  almost  sure  to 
occur,  unless  those  using  the  water  are  sufficiently 
intelligent  and  well  informed  to  take  the  precaution 
of  sterilising,  by  heat,  all  water  used  for  drinking 
purposes.  When  this  is  done  there  is  little  liability 
to  infection  through  other  channels,  with  the  excep- 
tion of  the  milk  supply — which  should  also  be  steril- 
ised by  heat — and  the  danger  from  flies  already 
referred  to.  This  latter  source  of  infection  is  to  be 
guarded  against  by  a  strict  sanitary  police,  by  which 
all  exposed  excreta  are  covered  with  earth  or  dis- 
infected, and  by  the  use  of  fly  screens  and  other 


120  INFECTION  AND  IMMUNITY 

methods  of  getting  rid  of  these  dangerous  domestic 
pests.  But  the  most  important  sanitary  precaution 
consists  in  the  immediate  disinfection  of  all  cholera 
excreta.  This  should  be  effected  so  far  as  possible 
in  the  sick-room  or  its  immediate  vicinity.  And  the 
dangerous  mild  cases  of  choleraic  diarrhoea  should  be 
looked  for  and  placed  under  treatment,  an  important 
part  of  which  will  be  complete  rest  and  isolation 
under  conditions  which  admit  of  the  necessary  meas- 
ures of  disinfection. 

A  channel  of  infection  not  yet  mentioned,  is 
through  the  soiled  underclothing  or  bed  linen  of 
cholera  patients.  Laundresses  have  not  infrequently 
contracted  the  disease  as  a  result  of  handling  such 
infected  articles.  For  this  reason  disinfection  by  im- 
mersion in  boiling  water  or  a  suitable  disinfecting 
solution  should  be  carried  out  in  the  sick-room,  or  an 
adjoining  apartment. 

The  cholera  germ,  which  was  discovered  by  the 
German  bacteriologist,  Dr.  Robert  Koch,  in  1884,  is 
usually  seen  in  the  form  of  slightly  curved  rods,  re- 
sembling somewhat  a  comma,  and  was  first  spoken  of 
as  "  the  comma  bacillus  of  Koch."  But  these  slightly 
curved  rods  may  grow  out  into  longer  or  shorter 
spiral  filaments,  and  the  so-called  comma  bacillus  is 
described  in  systematic  works  upon  bacteriology  as  a 
"spirillum"  (Spirillum  cholera  Asiatics).  It  is  con- 


ASIATIC  CHOLERA 


121 


stantly  found  in  the  excreta  of  persons  suffering  from 
cholera,  in  the  mild  cases  of  choleraic  diarrhoea 
as  well  as  in  the  severe  and  fatal  form  of  the  disease. 
Fortunately  for  the  human  race,  this  cholera  spirillum 
is  a  tender  exotic  which  has  not  succeeded  in  estab- 
lishing itself  permanently  in  Europe  and  America. 
Although  not  killed  by  cold,  its  epidemic  extension  is 


I'/  i 


.  ( 


^i 


to  *'  s  ^    '  *<?\ 

>  -    '_«•  A  -  +  tf** 
c  n,       ,  'J »  V  ^  ^ 


V     ' 

ti  v'  >   *    i,    * 
°»    ,»T?;      § 

FIG.  2.     Spirillum  of  Asiatic  cholera  ("  comma  bacillus  of  Koch  ") ;  magni- 
fied jooo  diameters. 


arrested  upon  the  approach  of  winter ;  and  our  brief 
historical  review  of  its  prevalence,  outside  of  its  home 
in  India,  shows  that  after  a  period  of  longer  or 
shorter  duration  the  disease  dies  out  and  does  not 
occur  again  independently  of  a  fresh  importation. 
Under  favourable  conditions  as  to  temperature,  the 
cholera  spirillum  multiplies  in  well  or  river  water, 


122  INFECTION  AND  IMMUNITY 

especially  if  this  contains  a  certain  amount  of  organic 
impurities.  It  has  been  shown  by  experiment  that  it 
will  multiply  abundantly  in  distilled  water  to  which 
from  two  to  three  per  cent,  of  bouillon  has  been 
added,  also  that  it  may  preserve  its  vitality  in  steril- 
ised well  or  river  water  for  several  months.  Koch 
found  in  his  early  investigations  that  rapid  multipli- 
cation may  occur  upon  the  surface  of  moist  linen.  In 
a  moist  condition  the  cholera  spirillum  may  retain 
its  vitality  for  months.  It  is  therefore  evident  that 
there  is  danger  of  its  being  carried  to  remote  local- 
ities in  bed  linen  or  underclothing  soiled  by  cholera 
discharges,  if  such  articles  in  a  moist  condition  are 
packed  up,  without  disinfecting,  to  be  transported  with 
other  personal  effects  of  immigrants.  Exposure  to  a 
temperature  of  140°  Fahr.  (60°  C.)  destroys  the  cholera 
spirillum  very  promptly.  It  is  also  quickly  killed  by 
desiccation  and  by  exposure  to  direct  sunlight — two 
to  four  hours'  exposure.  Experiments  made  in  Dr. 
Koch's  laboratory  show  that  it  is  killed  in  two  hours 
by  sulphuric  acid  or  hydrochloric  acid  diluted  in  the 
proportion  of  one  part  to  1300  parts  of  water;  by 
carbolic  acid  1:400  ;  by  lysol  i :  500  ;  by  corrosive  sub- 
limate 1:10,000;  by  sulphate  of  copper  1:500.  Solu- 
tions of  this  strength  would  disinfect  soiled  linen,  but 
in  practice  it  will  be  best  to  use  the  agents  mentioned 
in  much  stronger  solutions — one-per-cent.  solutions 


ASIATIC  CHOLERA  123 

of  carbolic  acid,  lysol,  or  sulphate  of  copper,  or  one 
part  of  corrosive  sublimate  to  1000  of  water.  For 
the  disinfection  of  cholera  excreta,  milk  of  lime  is  to 
be  recommended  (see  page  59),  or  a  five-per-cent. 
solution  of  carbolic  acid  or  lysol,  or  a  two-per-cent. 
solution  of  chloride  of  lime,  or  boiling  water. 

Sanitarians  no  longer  have  any  great  apprehension 
with  reference  to  the  extension  of  this  Asiatic  plague 
in  European  countries  or  in  America  The  measures 
for  its  prevention  are  simple  and  easily  applied,  and 
it  is  only  in  localities  where  ignorance  or  prejudice 
stands  in  the  way  of  the  execution  of  these  means  that 
the  deadly  spirillum  is  likely  to  establish  itself  in 
civilised  countries.  The  measures  referred  to  may 
be  summed  up  briefly  as  follows  :  Isolation  of  the 
sick,  including  all  cases  of  choleraic  diarrhoea  ;  disin- 
fection of  excreta  ;  sanitary  police  of  infected  locali- 
ties ;  boiling  of  drinking  water ;  exclusion  of  flies 
from  dwellings,  and  especially  from  kitchens. 

The  last-mentioned  sanitary  precaution  is  perhaps 
the  most  difficult  of  execution.  But,  fortunately,  it 
is  not  essential  when  the  measures  previously  men- 
tioned have  been  carried  out,  especially  the  disinfec- 
tion of  excreta.  Indeed  all  other  measures  might  be 
neglected  as  superfluous  if  we  could  be  assured  of 
the  complete  destruction  of  all  cholera  germs  in  the 
excreta  of  infected  individuals.  And  if  this  could  be 


i24  INFECTION  AND  IMMUNITY 

accomplished  in  the  countries  where  the  disease  has 
its  permanent  habitat,  there  is  every  reason  to  believe 
that  its  complete  extinction  would  soon  be  effected. 

The  prevention  of  cholera  by  "  protective  inocula- 
tions "  has  been  tested  on  a  large  scale  in  Spain, 
during  the  epidemic  of  1885,  a°d  more  recently  in 
India,  by  the  method  of  Haffkine. 

Unfortunately  the  evidence  relating  to  the  value 
of  these  protective  inoculations  is  not  very  satisfac- 
tory. The  evidence,  however,  is  in  favour  of  the 
view  that  a  partial  and  temporary  immunity  may  be 
conferred  by  the  subcutaneous  injection  of  cultures 
of  the  cholera  germ.  We  should  not  expect  such 
inoculations  to  confer  an  absolute  immunity,  inas- 
much as  this  does  not  result  from  an  attack  of  the 
disease.  That  repeated  attacks  may  occur  in  the 
same  individual  is  well  established,  and  this  may  hap- 
pen during  a  single  epidemic,  as  was  observed  in  the 
last  Hamburg  epidemic. 

That  the  inoculated  are  not  exempt  from  attack 
is  shown  by  Haffkine's  statistics  with  reference  to  in- 
oculations made  by  him  in  India  (1895).  Five  hun- 
dred inoculated  individuals  gave  a  mortality  of  19,  or 
3.8  percent.,  while  among  1735  non-inoculated,  under 
similar  conditions,  the  mortality  was  6.5  per  cent.  In 
our  opinion  inoculation  as  a  method  of  prevention 
should  not  be  employed  on  a  large  scale  in  anticipa- 


ASIATIC  CHOLERA  125 

tion  of  an  epidemic,  as  it  is  far  less  reliable  than  the 
preventive  measures  heretofore  referred  to — disinfec- 
tion of  excreta,  boiling  of  drinking  water,  etc.  But 
for  individuals  who  are  required,  for  any  reason,  to 
remain  in  an  infected  locality  in  India  or  elsewhere, 
it  is  perhaps  worth  while  to  further  test  the  value  of 
this  method  of  prevention. 


CHAPTER    III 
TYPHOID    FEVER 

DUBONIC  plague,  Asiatic  cholera,  and  dysentery 
^  are  filth  diseases  which  appertain  especially 
to  the  populous  countries  of  the  Orient.  In  the 
present  chapter  we  shall  consider  a  filth  disease 
which  prevails  in  all  parts  of  the  civilised  world, 
and  which  continues  to  claim  its  annual  quota  of 
victims  notwithstanding  the  fact  that  we  know  its 
specific  cause  (germ),  its  mode  of  transmission,  and 
the  preventive  measures  which  if  thoroughly  carried 
out  would  soon  lead  to  its  extinction.  According  to 
the  last  census  return,  there  were  35,379  deaths  from 
typhoid  fever  in  the  United  States  during  the  census 
year  1900.  The  increase  in  mortality  over  the  num- 
ber in  1890  (27,056)  is  out  of  proportion  to  the 
increase  in  population,  notwithstanding  the  general 
improvement  in  the  sanitary  condition  of  towns  and 
cities.  This  is  no  doubt  due  to  the  continued  pollu- 
tion of  water  supplies  and  to  the  extension  of  this 

infectious  disease  in  rural  districts. 

126 


TYPHOID  FEVER  127 

As  the  typhoid  bacillus  is  contained  in  the  excreta 
of  the  sick,  no  single  agency  is  more  important  for 
the  prevention  of  this,  and  of  other  filth  diseases, 
than  the  use  of  properly  constructed  sewers  for  the 
reception  of  excreta  and  its  removal  from  the  vicinity 
of  human  habitations. 

Disease  germs  contained  in  human  excreta,  when 
this  is  conveyed,  by  flushing  or  otherwise,  to  properly 
constructed  sewers,  are  no  longer  dangerous  to  the 
community  where  these  sewers  are  located.  But 
they  may  be  capable  of  doing  serious  harm  to  other 
communities  if  the  sewers  empty  into  a  stream  the 
water  of  which  is  used  for  drinking  purposes. 

Sewers  had  come  into  use  and  had  the  warm 
endorsement  of  sanitarians  long  before  the  discovery 
of  the  germs  of  the  infectious  maladies  under  con- 
sideration, and  before  it  was  positively  known  that 
the  infectious  agents  in  these  diseases  are  contained 
in  the  discharges  from  the  bowels.  But  now  that 
we  have  an  exact  knowledge  of  the  causes  of  these 
diseases,  the  reason  for  the  beneficent  results  attend- 
ing the  use  of  sewers,  in  connection  with  an  ample 
and  pure  water  supply,  is  apparent.  It  may  be  safely 
asserted  that  a  city  or  town  having  a  complete  and 
satisfactory  sewer  system  and  a  pure  water  supply  is 
practically  immune  from  epidemics  of  cholera  or 
typhoid  fever,  provided,  of  course;  that  the  sewers 


128  INFECTION  AND  IMMUNITY 

are  used  for  the  purpose  for  which  they  are  in- 
tended, and  that  streets  and  back  yards  no  longer 
serve  as  receptacles  for  filth,  as  was  usual  during  the 
presanitary  period,  even  in  great  cities  like  London 
and  Paris.  The  axiom  tout  a  /'  tgout  now  governs 
the  practice  not  only  in  Paris  but  wherever  the  fun- 
damental principles  of  sanitation  are  understood  and 
sewers  have  been  constructed. 

Unfortunately,  the  cost  of  sewer  construction,  the 
reluctance  of  taxpayers  to  part  with  their  money,  and 
the  ignorance  or  indifference  of  municipal  authorities 
have  conspired  to  prevent  the  accomplishment  of  this 
fundamental  sanitary  measure  in  very  many  towns  in 
the  United  States,  and  our  endemic  plague  — typhoid 
fever  —  continues  to  claim  a  large  annual  quota  of 
victims  in  such  localities.  Even  in  the  national  capital 
our  sewer  system  is  incomplete,  and  in  many  out-of- 
the-way  places,  especially  in  the  densely  populated 
alleys  of  the  city,  shallow  box  privies  are  in  use  as 
receptacles  for  human  excreta.  The  typhoid-fever 
rate,  owing  to  this  and  other  causes,  is  disgracefully 
high. 

Mortality  rates  in  towns  and  cities  throughout  the 
civilised  world  depend  to  a  large  extent  upon  the 
purity  of  the  water  supply  and  the  efficiency  of 
the  system  of  sewage  disposal ;  and  the  constant  im- 
provement which  is  shown  by  the  mortality  statistics 


TYPHOID  FEVER  129 

of  England  and  other  countries  which  have  made  the 
most  progress  in  this  direction  is  undoubtedly  largely 
due  to  these  two  factors.  This  is  well  illustrated  by 
the  mortality  statistics  of  armies.  In  the  German 
army,  the  annual  death-rate  in  1868  was  6.9  per  thou- 
sand, a  decade  later  it  was  4.82,  in  1888  it  had  fallen 
to  3.24,  and  in  1896  to  2.6.  In  our  own  army,  the 
death-rate  during  the  period  of  peace  just  prior  to  the 
Mexican  War  (1848)  was  about  three  and  one-half 
times  as  great  as  durmg  the  five  years  preceding 
our  recent  war  with  Spain  ;  and  since  the  year  1872 
there  has  been  a  diminution  of  the  death-rate  of 
nearly  forty  per  cent.  In  the  British  army  at  home 
stations,  the  mortality  rate  during  the  decade  end- 
ing in  1884  was  7-2  Per  thousand,  in  1889  the  rate 
had  fallen  to  4.57,  and  in  1897  to  3.42.  In  the 
Italian  army  there  has  been  a  gradual  and  progres- 
sive reduction  from  13.3  per  thousand  in  1875  to  4-2 
in  1897.  The  mortality  in  the  French  army  was 
a  little  over  21  per  thousand  during  the  five  years 
ending  in  1825.  In  1890  it  had  fallen  to  5.81  per 
thousand. 

According  to  the  best  estimates,  the  average  of 
human  life  in  the  sixteenth  century  was  somewhat 
less  than  twenty  years  ;  at  the  present  time  it  is 
more  than  twice  as  long  ;  and  during  the  past  twenty- 
five  years  the  average  duration  of  life  has  been 


'3° 


INFECTION  AND  I  MM  UNITY 


lengthened  about  six  years.  During  the  first  thirty- 
five  years  of  the  past  century,  the  vital  statistics  of  the 
city  of  London  showed  a  mortality  of  about  29  per 
thousand.  At  the  present  time  the  mortality  in  that 
great  city  has  been  reduced  to  from  17  to  19  per 
thousand. 

No  doubt  a  considerable  proportion  of  this  reduc- 
tion in  the  rate  of  mortality  in  London  and  in  other 
large  cities  in  this  country  and  in  Europe  is  due  to  a 
diminished  typhoid-fever  rate.  Indeed,  sanitarians 
at  the  present  day  depend  largely  upon  this  factor  of 
the  general  mortality  rate  of  cities  as  an  index  of  their 
sanitary  condition.  The  following  table  showing  the 
typhoid  death-rate  of  cities,  compiled  by  the  Register 
of  Vital  Statistics  of  the  New  York  Health  Depart- 
ment, is  given  in  a  recent  publication. 


AMERICAN  CITIES 


POPULATION. 

DEATHS. 

DEATH-RATE  PER 
10,000  INHABI- 
TANTS. 

Washington  

278,7l8 

161 

«5.78 

Chicago  

i.6o8,s;7q 

500 

3.00 

Boston  • 

C7"Z,C7Q 

142 

2.48 

Philadelphia  

1.  3  21  408 

444 

Vl6 

Providence  

178.000 

47 

2.04 

New  York  

i  ci6.qi7 

727 

2.06 

St.  Louis  

coS  ooo 

108 

7.  -2  I 

San  Francisco  

360  ooo 

70 

I.  Q4 

TYPHOID  FEVER 
FOREIGN  CITIES 


POPULATION. 

DEATHS. 

DEATH-RATE  PER 
10,000  INHABI- 
TANTS. 

Belfast      

•5C  I    08"? 

"?4O 

9O4 

St   Petersburg  

oO  *»W**O 

I  24.8  64.3 

o^y 
I  060 

•VT- 
8  4.0 

Cairo  

608  QIO 

48^ 

"•T-y 

7  06 

Glasgow         

764.  467 

108 

2  c;o 

Liverpool  

686  41:4 

i  y«j 

i6c 

*O!r 

2  41 

Dublin  

376  081 

ivj 
1  04 

2  77 

London  

4.^44  08^ 

54-8 

121 

Paris  

2  660  £\  ^Q 

?A-2 

I   2Q 

Berlin  

•^""^OOV 
I  80  1  QOO 

JT-O 

88 

j  .^y 

O  47 

Vienna  

I  7?C  740 

76 

O  44 

Munich    

CO"?  OOO 

24 

0  48 

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w.^.<j 

The  high  typhoid-fever  death-rate  in  the  city  of 
Washington  is  probably  due  in  part  to  the  contamina- 
tion of  its  water  supply  and  in  part  to  the  fact  that 
its  sewer  system  is  still  incomplete.  Congress  has 
recently  appropriated  money  for  a  sand-filtration 
plant,  such  as  is  now  in  use  for  London  and  various 
European  cities,  and  it  is  hoped  that  within  a  few 
years,  at  least,  the  typhoid  mortality  may  compare 
more  favourably  with  that  of  London,  Paris,  Berlin, 
Vienna,  and  Munich,  as  shown  in  the  above  table. 

The  typhoid-fever  death-rate  per  10,000  of  inhabit- 
ants in  the  city  of  Chicago  was  9.16  in  1890  and 
1 7.38  in  the  following  year.  This,  however,  represents 
an  unusual  epidemic  prevalence  of  the  disease,  which 
was  continued  into  the  following  year  (12.06  per 


I32  INFECTION  AND  IMMUNITY 

10,000),  after  which  a  gradual  reduction  occurred  until 
the  census  year  1900,  when  the  very  low  rate  of 
1.98  was  reached.  In  New  York  the  typhoid  rate 
was  4.47  per  10,000  inhabitants  in  1870,  and  it  has 
only  slightly  exceeded  this  figure  in  two  years  since 
that  date  (4.77  in  1881  and  4.72  in  1883).  Since 
1893  it  has  been  constantly  below  2  per  10,000  inhabit- 
ants, a  rate  which  probably  to  a  large  extent  repre- 
sents cases  in  which  infection  occurred  outside  of  the 
city  at  summer  resorts,  etc. 

In  Philadelphia  the  typhoid  death-rate  has  been 
constantly  above  that  of  New  York,  as  might  be  ex- 
pected from  the  superior  advantages  enjoyed  by  the 
last-named  city  in  its  water  supply  —  from  the  Croton 
River.  The  highest  typhoid  death-rate  recorded  for 
the  city  of  Philadelphia  during  the  past  thirty  years 
was  9.22  per  10,000  in  the  year  1876,  the  lowest  3.24 
in  the  year  1894.  The  average  has  been  about  5.6, 
which  is  but  little  below  the  death-rate  for  the  city  of 
Washington  in  the  year  1900  as  given  in  the  above 
table. 

In  Boston  the  typhoid  mortality  has  fluctuated 
between  8.62  per  10,000  in  1872  and  2.55  in  1900,  the 
latter  rate  being  the  lowest  recorded  during  a  period 
of  thirty  years. 

Without  doubt  a  majority  of  typhoid-fever  epi- 
demics are  due  to  infection  of  the  water  supply  by 


TYPHOID  FEVER  133 

typhoid  excreta.  A  good  example  of  a  severe  epi- 
demic directly  traceable  to  such  contamination  is  af- 
forded by  the  recent  epidemic  at  Ithaca,  N.  Y.,  during 
which  912  cases  with  58  deaths  occurred  during  the 
months  of  January,  February,  and  March,  1903  ;  128 
cases  and  26  deaths  occurred  among  the  students  at- 
tending Cornell  University. 

The  fatal  epidemic  which  occurred  at  Plymouth, 
Pa.,  some  years  ago,  has  been  traced  to  the  pollution 
of  the  water  supply  by  the  excreta  of  a  single  case  of 
typhoid  fever,  and  this  notwithstanding  the  fact  that 
the  water  passed  through  three  storage  reservoirs, 
having  altogether  a  capacity  of  5,000,000  gallons. 
During  this  epidemic  1 104  cases  were  recorded  with 
a  mortality  of  114. 

Without  doubt  typhoid  fever  is  sometimes  spread 
by  means  of  infected  dust  containing  living  typhoid 
bacilli  in  desiccated  excreta  of  typhoid  patients.  This 
is  one  of  the  ways  in  which  the  disease  is  spread 
among  new  levies  of  troops.  It  has  been  shown  by 
experiment  that  the  typhoid  bacillus  may  retain  its 
vitality  when  mixed  with  dry  earth  for  a  period  of  at 
least  twenty-five  days. 

There  is  a  good  reason  to  believe  that  in  several  of 
our  camps,  during  the  Spanish-American  War,  this 
was  an  important  factor  in  the  etiology  of  typhoid- 
fever  epidemics.  The  average  mortality  from  typhoid 


134  INFECTION  AND  IMMUNITY 

fever  in  our  regular  army  since  the  Civil  War  has 
been:  For  the  first  decade  (1868-1877),  9.5  per 
10,000  of  mean  strength  ;  for  the  second  decade 
(1878-1887),  10.8  per  10,000;  for  the  third  decade 
(1888-1897),  5.5  per  10,000.  This  last  rate  com- 
pares favourably  with  that  of  many  of  our  principal 
cities  :  for  example,  it  is  exceeded  by  the  typhoid 
death-rate  of  the  city  of  Washington,  which  is  7.81 
per  10,000  (average  of  ten  years,  1888-1897);  by  that 
of  the  city  of  Chicago,  which  is  6.44  per  10,000;  by 
that  of  Pittsburg,  which  is  8.8  per  10,000.  As  a  re- 
sult of  .unsanitary  conditions  existing  in  the  camps  in 
which  our  troops  were  hastily  assembled  at  the  outset 
of  the  Spanish-American  War,  the  typhoid  death-rate 
in  our  army  of  volunteers  and  regulars  during  the 
year  ending  April  30,  1899,  was  more  than  twenty- 
two  times  as  great  as  it  had  been  in  our  regular  army 
during  the  decade  immediately  preceding  the  war 
period.  As  compared  with  the  Civil  War,  however, 
there  was  a  decided  improvement,  the  typhoid  mor- 
tality for  the  first  year  of  the  Civil  War  having  been 
197.1  per  10,000  of  mean  strength  and  for  the  Span- 
ish-American War  123.7  per  10,000. 

Experience  shows  that  new  levies  of  troops  are  es- 
pecially subject  to  typhoid  fever  and  other  infectious 
"  camp  diseases,"  not  only  because  of  lack  of  disci- 
pline and  consequent  difficulty  in  the  enforcement  of 


TYPHOID  FEVER  135 

sanitary  regulations,  but  also  because  the  individual 
soldiers  are  very  susceptible  to  infection,  owing  to 
their  age,  the  abrupt  change  in  their  mode  of  life,  the 
exposure  and  fatigue  incident  to  camp  life,  and  last, 
but  not  least,  their  own  imprudence  as  regards  eating, 
drinking,  exercise,  etc.  In  the  absence  of  sewers  or 
other  adequate  means  of  removing  excreta,  the  camp 
site  is  likely  to  become  infected  by  the  discharges  of 
unrecognised  cases  of  typhoid  fever,  and  typhoid  ba- 
cilli are  carried  by  flies  to  the  kitchen  and  mess-tents 
and  deposited  upon  food,  or  as  dust  are  directly  de- 
posited upon  the  mucous  membranes  of  the  respira- 
tory passages  of  those  living  in  the  infected  camp. 

It  must  be  remembered,  also,  that  typhoid  bacilli 
are  frequently  present  in  great  numbers  in  the  urine 
of  typhoid-fever  cases,  and  that  this  is  a  prolific  source 
of  infection  of  the  ground  under  the  conditions  exist- 
ing in  camps.  The  presence  of  typhoid  bacilli  in 
immense  numbers  in  the  urine  of  convalescents  from 
typhoid  has  been  repeatedly  demonstrated,  and  in 
view  of  this  fact  it  is  evident  that  measures  of  disin- 
fection should  be  continued  until  all  danger  of  propa- 
gating the  disease  in  this  way  has  passed. 

The  outbreaks  of  typhoid  fever  in  cities,  which 
have  frequently  been  traced  to  infected  milk,  and  in 
which  the  cases  are  often  limited  to  those  who  use 
the  milk  from  a  particular  dairy,  are  primarily  due  to 


136  INFECTION  AND  IMMUNITY 

infected  water  used  to  dilute  the  milk  or  to  wash  the 
vessels  containing  it. 

The  bacillus  of  typhoid  fever  is  a  rod-shaped  micro- 
organism, about  one  fifty-thousandth  of  an  inch  thick 
(from  five-  to  eight-tenths  of  a  micro-millimetre)  and 
from  two  to  six  times  as  long  as  it  is  broad  ;  it  also 


FIG.  3.     Bacillus  of  typhoid  fever  ;  magnified  1000  diameters. 

grows  out  into  long  thread-like  filaments.  The  mi- 
nute size  of  this  and  other  similar  disease  germs  will 
perhaps  be  better  appreciated  when  we  say  that  one 
cubic  centimetre  of  urine  from  a  typhoid  patient  has 
been  found  to  contain  as  many  as  1 72,000,000  typhoid 
bacilli — estimated  by  a  counting  method  well  known 
to  bacteriologists. 

This  bacillus  was  first   observed  in   1880  by  the 
German  physician  and  bacteriologist,  Eberth,  and  in- 


TYPHOID  FEVER  137 

dependently  by  Koch.  That  it  is  the  veritable  germ 
of  the  infectious  disease  known  as  typhoid  fever  has 
been  demonstrated  by  subsequent  researches  and  is 
now  generally  admitted.  This  bacillus  grows  readily 
in  milk,  in  beef  tea,  and  in  other  culture  media  usually 
employed  by  bacteriologists.  It  is  killed  by  a  few 
minutes'  exposure  to  a  temperature  of  140°  Fahr. 
(60°  C.),  but  unlike  the  cholera  spirillum  is  not  readily 
destroyed  by  desiccation,  having  been  preserved  in 
dry  and  pulverised  soil  for  a  period  of  twenty-five 
days.  It  may  preserve  its  vitality  in  sterilised  water 
for  four  weeks  or  more,  and  in  typhoid  excreta  for  at 
least  three  months.  It  has  been  recovered  by  culti- 
vation from  earth,  upon  which  bouillon  cultures  had 
been  poured,  after  an  interval  of  five  and  one-half 
months ;  and  from  soil  which  had  been  manured 
with  the  undisinfected  discharges  of  typhoid  patients 
after  these  discharges  had  remained  in  a  pit  during 
five  winter  months. 

These  facts  make  it  apparent  why  typhoid  fever 
has  become  so  widely  disseminated  throughout  the 
world  and  why  it  is  the  principal  endemic  filth  disease 
in  the  United  States.  A  primitive  and  sparse  popula- 
tion, which  obtains  its  drinking  water  chiefly  from 
live  springs  and  running  streams,  is  less  liable  to 
suffer  from  this  disease  than  the  permanent  denizens 
of  towns  which  are  destitute  of  sewers  and  which 


138  INFECTION  AND  IMMUNITY 

depend  upon  shallow  wells  or  polluted  streams  for 
their  supply  of  drinking  water.  The  liability  to 
dangerous  soil  pollution  in  the  vicinity  of  human 
habitations,  or  in  temporary  camps,  is  so  great  that 
sanitarians  have  long  since  learned  to  look  with  sus- 
picion upon  wells  located  in  towns  or  in  the  vicinity 
of  privy-vaults  in  the  country.  Numerous  examples 
are  upon  record  of  local  outbreaks  of  typhoid  fever 
directly  traceable  to  the  drinking  of  contaminated 
well-water. 

The  typhoid  bacillus  is  promptly  destroyed  by  the 
various  chemical  disinfectants  named  in  the  pre- 
vious chapter  as  germicidal  for  the  cholera  spirillum. 
From  a  practical  point  of  view,  for  the  disinfection  of 
excreta,  we  recommend  especially  milk  of  lime,  carbolic 
acid  (five-per-cent.  solution),  chloride  of  lime  (four-per- 
cent, solution),  lysol,  cresol  or  creolin  (two-per-cent. 
solution).  The  quantity  of  the  disinfecting  solution 
used  should  be  in  excess  of  the  quantity  of  excreta 
to  be  disinfected,  and  the  time  allowed  for  the  action 
of  the  germicidal  agent  should  be  at  least  two  hours. 

Boiling  water  in  liberal  amount  (four  or  five  times 
the  quantity  of  liquid  excreta  and  urine)  may  also  be 
used  with  perfect  safety  and  will  accomplish  the  ob- 
ject in  view  within  a  few  minutes  (ten  minutes). 
For  bed  linen  and  soiled  underclothing,  immersion  in 
boiling  water  or  in  a  two-per-cent.  solution  of  one  of 


TYPHOID  FEVER  139 

the  coal-tar  products  above  mentioned  is  to  be  recom- 
mended (carbolic  acid,  lysol,  creolin,  or  tricresol). 

The  prevention  of  typhoid  fever  by  protective  in- 
oculations has  been  tested  on  a  large  scale,  by  sur- 
geons of  the  English  army,  in  India  and  in  South 
Africa.  Sterilised  cultures  of  the  typhoid  bacillus 
are  used  for  this  purpose.  The  inoculation  gives  rise 
to  local  tumefaction  and  to  more  or  less  general  dis- 
turbance of  brief  duration.  It  is  recommended  that 
a  second  inoculation  be  practised  at  the  end  of  a 
week.  Wright,  the  originator  of  the  method,  re- 
ports that  among  11,295  British  soldiers  inoculated 
in  India,  the  percentage  of  those  who  subsequently 
contracted  typhoid  fever  was  0.95,  while  2.5  per  cent, 
of  those  not  inoculated  suffered  an  attack  of  the 
disease.  The  soldiers  in  South  Africa,  during  the 
Boer  War,  who  had  been  inoculated  are  reported  to 
have  suffered  attacks  of  typhoid  in  the  proportion 
of  six  per  thousand,  while  those  not  inoculated  suf- 
fered to  the  extent  of  nine  per  thousand.  The  dif- 
ference is  not  sufficiently  great  to  give  confidence  in 
inoculations  by  Wright's  method  as  a  reliable  pre- 
ventive measure.  In  this  disease,  as  in  cholera  and 
bubonic  plague,  our  main  reliance  should  be  upon  the 
sanitary  measures  heretofore  referred  to,  and  espe- 
cially upon  disinfection  of  excreta  and  sterilisation 
of  drinking  water. 


CHAPTER  IV 

DYSENTERY,  CHOLERA  INFANTUM,  ETC. 

pvYSENTERY  and  the  fatal  form  of  "summer 
^^^  complaint,"  so  common  among  the  poorer 
classes  in  cities,  are  due  to  a  bacillus  which  resembles 
in  many  respects  the  bacillus  of  typhoid  fever,  but 
which  nevertheless  presents  certain  specific  differ- 
ences which  can  be  recognised  by  the  expert  bacterio- 
logist. As  this  bacillus  is  found  in  the  excreta  of 
the  sick  and  an  attack  of  either  disease  depends 
upon  the  introduction  of  the  germ  to  the  intestinal 
tract,  by  way  of  the  mouth,  we  must  include  dysen- 
tery and  cholera  infantum  among  the  filth  diseases. 
There  is  another  form  of  tropical  dysentery  due  to  a 
parasite  of  a  different  class  (amoebic  dysentery),  but 
this  is  also  propagated  in  the  same  way  and  its  pre- 
vention calls  for  the  same  sanitary  measures.  These 
are  identical  with  the  measures  already  recommended 
in  previous  chapters  for  the  prevention  of  cholera 
and  of  typhoid  fever.  The  victims  of  cholera  in- 

140 


DYSENTERY,  CHOLERA  INFANTUM,  ETC.     141 

fantum  are  no  doubt  usually  infected  through  the 
medium  of  milk,  which  becomes  contaminated  either 
at  the  dairy  or  after  it  has  been  brought  to  the  city— 
in  some  cases  no  doubt  by  flies  which  have  been  in 
contact  with  the  discharges  from  the  bowels  of  other 
patients  similarly  affected. 

In  Oriental  countries  where  human  excreta  are  used 
to  fertilise  the  soil  for  growing  lettuce,  and  other 
vegetables  which  are  eaten  without  cooking,  it  is  be- 
lieved that  dysentery  is  not  infrequently  contracted 
through  the  medium  of  such  vegetables. 

In  tropical  and  semi-tropical  countries  dysentery 
claims  more  victims  than  typhoid  fever,  which  pre- 
vails more  extensively  in  regions  lying  within  the 
temperate  zone.  Among  English  soldiers  serving  in 
India  and  China,  more  deaths  occur  from  dysentery 
alone  than  from  all  diseases  among  troops  at  home 
stations. 

United  States  troops  in  the  Philippine  Islands  have 
suffered  severely  from  tropical  dysentery,  which  con- 
stitutes the  principal  cause  of  mortality. 

The  death-rate  per  thousand  from  "  diarrhceal  dis- 
eases "  among  our  soldiers  in  the  Philippines  during 
the  year  1900  was  2.02,  while  in  the  United  States  it 
was  o.  1 2.  Epidemics  of  dysentery  have,  however,  fre- 
quently occurred  within  the  limits  of  the  United  States, 
and  during  our  Civil  War  this  and  other  forms  of  intes- 


142  INFECTION  AND  IMMUNITY 

tinal  flux  (chronic  diarrhoea)  caused  a  large  share  of 
the  mortality  among  the  troops,  on  both  sides,  in 
that  momentous  struggle.  Deposits  of  infected 
excreta  upon  the  surface  of  the  ground  or  in  shal- 
low pits  ;  neglect  of  camp  sanitation  ;  the  mischievous 
activity  of  flies,  which  often  constitute  a  veritable 
pest  under  such  conditions  ;  contamination  of  the 
water  supply ;  and  the  deposit  of  dust  from  the  in- 
fected camp  site  upon  the  moist  mucous  membrane 
of  the  air  passages,  are  the  chief  factors  in  the  pro- 
pagation of  all  the  infectious  filth  diseases — that  is,  in 
those  diseases  in  which  the  disease-producing  germ  is 
present  in  the  excreta.  We  might  include  here  cer- 
tain diseases  due  to  the  presence  of  parasitic  worms 
in  the  intestine,  the  ova  of  which  are  discharged  with 
the  excreta.  Recent  researches  show  that  a  disease 
characterised  by  persistent  anaemia  and  debility  and 
often  ascribed  to  "  malaria,"  which  is  very  common  in 
many  of  the  Southern  States,  is  due  to  a  minute  intes- 
tinal worm  (  Uncinaria  americand).  Dr.  Stiles,  of  the 
Public  Health  and  Marine  Hospital  Service,  to  whom 
we  owe  this  discovery,  says  :  "  I  have  now  examined 
specimens  of  this  new  parasite  from  Virginia,  Texas, 
Cuba,  and  Porto  Rico.  The  clinical  picture  of  the 
disease  does  not  differ  from  that  of  the  malady  caused 
by  the  Old  World  parasite  Uncinaria  duodenalis" 
The  vast  importance  of  the  measures  recommended 


DYSENTERY,  CHOLERA  INFANTUM,  ETC.     143 

for  the  prevention  of  the  various  filth  diseases  here- 
tofore referred  to  will  be  appreciated,  when  the  fact 
is  taken  into  consideration  that  in  our  great  Civil  War 
nearly  as  many  deaths  resulted  from  these  diseases  as 
from  wounds  inflicted  in  battle. 

During  jhe  Civil  War  the  number  of  deaths  from 
disease  in  the  Union  army  was  186,216;  the  number 
killed  in  battle  or  who  died  of  wounds  was  93,969. 
The  number  of  deaths  from  the  several  forms  of 
diarrhoea  and  dysentery  was  44,558,  the  number  due 
to  "  camp  fevers,"  including  typhoid,  "  typho-malarial," 
etc.,  was  40,656, — a  total  of  85,214.  This  is  also  the 
history  of  wars  in  other  countries  and  in  all  ages — 
disease  claims  more  victims  than  battle.  When  we 
add  to  the  deaths  resulting  from  filth  diseases  in  the 
armies  of  the  world  the  enormous  mortality  which 
has  occurred  and  continues  to  occur  among  the  civil 
population,  the  figures  are  astounding.  And  yet 
these  diseases  are  now  generally  recognised  as  "  pre- 
ventable diseases  "  ;  and,  as  shown  in  previous  chap- 
ters, great  success  has  already  attended  the  efforts 
made  by  sanitarians  to  restrict  their  prevalence.  In 
the  United  States  army,  during  the  Spanish- American 
War,  typhoid  fever  prevailed  extensively  in  nearly  all 
our  camps  among  the  new  levies  of  troops,  but  with- 
in a  few  months  its  ravages  were  checked  by  the 
enforcement  of  proper  sanitary  measures.  In  the 


144  INFECTION  AND  IMMUNITY 

Philippine  Islands,  owing  to  the  difficulties  encount- 
ered in  the  execution  of  well-known  preventive  meas- 
ures, there  has  been  considerable  mortality  from  filth 
diseases.  But  when  we  consider  that  our  troops 
have  been  engaged  in  active  operations  in  a  tropical 
country,  where  all  forms  of  intestinal  flux  are  preval- 
ent, and  where  they  have  been  more  or  less  exposed 
to  infection  by  the  germs  of  cholera  and  bubonic 
plague  as  well  as  by  that  of  typhoid  fever,  it  is  safe  to 
say  that  the  sanitary  record  of  our  army  in  the  Philip- 
pines is  unsurpassed  by  that  of  any  other  body  of 
troops  which  has  been  exposed  in  a  tropical  country 
under  similar  conditions. 


CHAPTER  V 

RELAPSING  FEVER 

D ELAPSING  fever  is  one  of  the  pestilential  dis- 
eases  which  has  contributed  considerably  to 
the  mortality  of  Europe,  especially  during  times  of 
famine.  It  was  not  clearly  recognised  as  a  distinct 
disease  until  the  eighteenth  century,  and  it  is,  there- 
fore, impossible  to  say  to  what  extent  it  may  have 
prevailed  prior  to  that  time. 

The  first  clearly  recorded  epidemic  occurred  in  Ire- 
land in  1 739,  but  the  literature  relating  to  the  disease 
belongs  mostly  to  the  nineteenth  century.  The  fact 
that  the  disease  was  not  recognised  previously  to  the 
date  above  mentioned  cannot  be  taken  as  evidence 
that  it  did  not  exist.  Typhoid  and  typhus  fevers  had 
not  been  differentiated  as  distinct  diseases  at  this 
time  ;  and,  as  all  of  these  diseases  are  likely  to  pre- 
vail simultaneously  when  insanitary  conditions  exist, 
especially  in  densely  populated  countries  and  in  times 
of  scarcity  of  food,  it  is  probable  that  all  of  these 

10 

145 


146  INFECTION  AND.  IMMUNITY 

diseases  had  a  share  in  contributing  to  the  mortality 
statistics  of  Europe  and  Asia  during  the  Middle  Ages 
and  in  earlier  times. 

Relapsing  fever  prevailed  in  Ireland  and  in  Scot- 
land during  the  years  1799-1800,  1817-19,  1826- 
27,  1842-48,  and  in  the  last  year  (1848)  it  invaded 
several  of  the  larger  towns  of  England.  In  1868- 
70  it  again  prevailed  in  England  and  Scotland,  and 
cases  are  reported  to  have  occurred  in  London  as 
recently  as  the  year  1873.  On  the  Continent  the  first 
accounts  we  have  come  from  Russia — Odessa,  in 
1833;  Moscow,  1840-41.  In  the  autumn  of  1863 
the  disease  reappeared  in  Odessa ;  the  following  year 
it  became  epidemic  over  extensive  areas  in  Russia, 
and  extended  to  Livonia  and  Finland  (1865),  to  Si- 
beria (1866),  and  to  Poland  (1868).  According  to 
Hirsch,  the  disease  continued  to  prevail  in  Russia 
over  extensive  areas  during  subsequent  years,  and 
was  observed  among  the  Russian  troops  as  late  as 
1878-79.  In  Germany  an  extensive  epidemic  broke 
out  in  1868,  as  a  result  of  importation  from  Russia. 
A  second,  more  restricted,  epidemic  occurred  in 
1871-72,  and  a  third  in  1878-79.  In  the  west  and 
south-west  of  Europe  —  Switzerland,  France,  Italy, 
Spain — the  disease  is  as  yet  unknown.  In  India  re- 
lapsing fever  has,  no  doubt,  prevailed  for  many  years, 
but  the  differential  diagnosis  between  it  and  remit- 


RELAPSING  FEVER  147 

tent  fever,  or  the  specific  continued  fevers  which  pre- 
vail there  so  largely,  was  not  clearly  made  out  by 
the  earlier  observers.  During  the  last  thirty  years, 
however,  numerous  outbreaks  of  this  disease  in  vari- 
ous parts  of  India  have  been  recorded,  and  Carter 
has  demonstrated  that  the  disease,  as  it  occurs  in  that 
country,  is  identical,  as  regards  its  clinical  history, 
with  relapsing  fever,  as  described  by  recent  European 
authorities  ;  and,  also,  that  it  is  characterised  by  the 
constant  presence  of  the  spirillum  discovered  by 
Obermeier  in  blood  drawn  during  a  febrile  paroxysm. 
Relapsing  fever  has  several  times  been  imported  to  the 
United  States,  but  its  prevalence  has  been  limited 
to  restricted  areas  in  our  largest  seaport  cities. 
In  1844  fifteen  cases  were  received  into  the  Phila- 
delphia Hospital  from  an  emigrant  ship  sailing  from 
Liverpool ;  in  1848  a  few  cases  arrived  in  New  York  ; 
and  in  1850-51  Dr.  Austin  Flint  saw  a  number  of 
cases,  among  recently  arrived  Irish  emigrants  received 
into  the  Buffalo  City  Hospital.  But  no  epidemic  re- 
sulted from  these  importations,  and  it  was  not  until 
some  years  later  (1869-70)  that  the  disease  became 
epidemic  in  certain  sections  of  the  cities  of  New  York 
and  Philadelphia.  Parry,  who  made  a  careful  investi- 
gation with  reference  to  the  origin  of  the  first  cases 
in  Philadelphia,  was  unable  to  trace  them  to  importa- 
tion ;  but  this  can  scarcely  be  questioned,  in  view  of 


148  INFECTION  AND  IMMUNITY 

what  is  known  of  the  history  and  etiology  of  the 
disease,  and  in  consideration  of  the  fact  that  Phila- 
delphia is  a  seaport  city  which  has  constant  communi- 
cation with  ports  on  the  other  side  of  the  Atlantic, 
which  at  that  time  were  known  to  be  infected.  The 
number  of  cases  reported  during  this  epidemic  in 
Philadelphia  was  1 1 76. 

The  coincidence  of  relapsing  fever  and  typhus  fever 
has  been  noted  in  many  of  the  epidemics  which  have 
occurred  in  Europe,  but  the  history  of  this  coincid- 
ence does  not  justify  the  supposition  that  there  is 
any  etiological  relation  between  these  diseases  other 
than  that  furnished  by  common  predisposing  causes, 
viz.,  the  depressing  effects  of  overcrowding,  insuffi- 
cient food,  and  filthy  surroundings.  This  view  is 
supported  by  the  fact  that  either  disease  may  occur 
alone,  and  the  circumstance  that  sometimes  one  and 
sometimes  the  other  has  the  precedence  in  time 
in  those  epidemics  in  which  coincidence  has  been 
observed. 

The  germ  of  relapsing  fever  was  discovered  in 
1873  by  Obermeier,  a  German  physician.  This  was 
the  first  discovery  of  the  specific  germ  of  an  infec- 
tious disease  peculiar  to  the  human  race,  and  opened 
the  way  for  the  subsequent  demonstration  of  the 
germs  of  leprosy  (1879),  typhoid  fever  (1880),  pneu- 
monia (1880),  tuberculosis  (1882),  cholera  (1884), 


RELAPSING  FEVER 


149 


diphtheria  (1884),  tetanus  (1884),  influenza  (1892), 
bubonic  plague  (1894),  dysentery  (1900). 

This  germ  is  a  slender  spiral  filament,  which  is 
found  in  the  blood  of  relapsing-fever  patients  during 
the  febrile  paroxysm.  The  presence  of  the  spirillum 
in  the  excreta  of  relapsing-fever  patients  has  not 
been  demonstrated,  but  it  can  scarcely  be  doubted 


FIG.  4.     Spirillum  of  relapsing  fever,  as  seen  in  the  blood  ;  magnified  1000 
diameters. 


that  this  disease  belongs  in  the  same  category  with 
typhoid  fever,  bubonic  plague,  and  Asiatic  cholera — 
i.  e.,  that  it  is  one  of  the  filth  diseases  and  is  spread 
principally  by  means  of  excreta  containing  the  spe- 
cific infectious  agent  or  germ.  It  may  be  that  the 
spirillum  of  relapsing  fever  produces  reproductive 
spores,  which  would  be  difficult  of  demonstration  in 


150  INFECTION  AND  IMMUNITY 

the  excreta.  Even  the  spirillum  itself  is  not  easy  to 
see.  A  good  microscope  and  a  considerable  degree 
of  skill  in  its  use  are  required  for  the  demonstration  of 
the  slender  spiral  filaments  in  blood  drawn  from  the 
circulation  of  a  relapsing-fever  patient.  Although 
comparatively  long  and  endowed  with  active  move- 
ments, they  are  only  about  one  fifty-thousandth  of  an 
inch  in  diameter. 

That  the  disease  may  be  transmitted  by  direct  con- 
tagion, from  individual  to  individual,  has  generally 
been  admitted  by  medical  authorities.  On  the  other 
hand,  the  evidence  on  record  shows  that  in  well  venti- 
lated apartments  and  hospital  wards  the  attendants 
upon  the  sick  and  patients  suffering  from  other  dis- 
eases are  not  very  liable  to  contract  the  disease. 
Where,  however,  the  sick  are  massed  together  in  in- 
sufficiently ventilated  hospitals,  or  when  cases  occur 
in  the  overcrowded  tenements  of  the  poor,  the  trans- 
mission of  the  disease  to  attendants  and  others  ex- 
posed to  contagion  is  far  more  frequent. 

Up  to  the  present  time,  attempts  to  reproduce  the 
spirillum  of  relapsing  fever  in  a  series  of  cultures 
have  not  been  successful. 

There  is  no  evidence  that  climate  or  season  has  any 
marked  influence  upon  the  prevalence  of  relapsing 
fever ;  the  disease  has  prevailed  in  Siberia  as  well  as 
in  India,  and  its  preference  for  certain  localities  is 


RELAPSING  FEVER  151 

quite  independent  of  climatic  conditions,  relating 
rather  to  circumstances  connected  with  the  mode 
of  life  and  hygienic  surroundings  of  the  population. 
No  age  is  exempt,  and  sex  has  no  apparent  influence ; 
but  children  are  more  subject  to  be  attacked  than 
adults,  and  susceptibility  seems  to  diminish  to  some 
extent  with  advancing  age.  According  to  Murchison, 
only  195  out  of  2111  cases  received  into  the  Lon- 
don Fever  Hospital,  in  twenty-three  years,  were  over 
fifty  years  of  age.  To  appreciate  the  value  of  these 
figures  it  would  evidently  be  necessary  to  know  how 
large  a  proportion  of  the  exposed  population  were 
over  fifty  years  of  age. 

Insufficient  food 'is  generally  recognised  by  medical 
writers  as  a  potent  predisposing  cause,  and  epidemics 
have  so  frequently  been  observed  to  coincide  with 
periods  of  unusual  scarcity  that  the  name  "  famine 
fever  "  has  been  applied  to  the  disease.  Some  authors 
have  even  gone  so  far  as  to  ascribe  to  starvation  and 
its  accompaniments  —  overcrowding  and  filthy  sur- 
roundings— an  essential  role  in  the  development  of 
the  disease.  But,  as  in  the  case  of  other  specific 
contagious  diseases,  there  seems  to  be  very  little 
foundation  for  the  idea  that  relapsing  fever  may  be 
developed  de  novo  in  times  of  famine,  and  its  epidemic 
prevalence  at  such  times  is  to  be  ascribed  rather  to 
increased  vulnerability,  on  the  part  of  the  starving 


152  INFECTION  AND  IMMUNITY 

population,  to  the  action  of  the  specific  exciting  cause 
of  the  disease.  We  know  that  under  favourable  hy- 
gienic conditions  the  disease  has  but  little  disposition 
to  spread,  and  that  in  the  severest  epidemics  it  finds 
its  victims  almost  exclusively  among  the  destitute. 
On  the  other  hand,  in  the  numerous  instances  in 
which  shipwrecked  mariners,  Arctic  explorers,  etc., 
have  been  subjected  to  absolute  starvation,  we  have 
no  account  of  the  development  of  any  such  disease  as 
relapsing  fever.  Overcrowding  is  considered  by  Parry 
to  be  a  more  potent  predisposing  cause  than  starva- 
tion, and  his  careful  study  of  the  circumstances  of 
those  who  were  taken  sick  during  the  prevalence  of 
the  disease  in  Philadelphia  (1870)  seems  to  justify 
this  conclusion  —  which  is,  moreover,  supported  by 
the  observations  of  Muirhead,  Bennett,  Lebert,  and 
others. 

One  attack  of  relapsing  fever  does  not  protect  the 
individual  from  subsequent  attacks,  and  second  or 
even  third  attacks  during  the  same  epidemic  have 
been  noted. 

What  has  been  said  with  reference  to  the  factors 
which  favour  the  epidemic  prevalence  of  the  disease 
will  indicate  the  proper  preventive  measures.  Mod- 
ern sanitary  science  has,  apparently,  banished  this 
disease  from  its  former  haunts  in  European  countries. 
It  has  not  been  introduced  into  the  United  States 


RELAPSING  FEVER  153 

since  the  epidemic  heretofore  referred  to,  which  oc- 
curred in  the  city  of  Philadelphia  in  the  years  1869- 
70.  Should  cases  of  the  disease  again  be  brought 
to  our  shores,  prompt  isolation  of  the  sick  and  the 
disinfection  of  excreta  would  probably  suffice  to  pre- 
vent its  extension 


CHAPTER  VI 

TYPHUS  FEVER 

T^YPHUS  fever,  also  known  as  "spotted  fever," 
"  ship-fever,"  etc.,  is  an  infectious  disease  which 
has  doubtless  prevailed  in  Europe  for  many  centuries, 
although  no  definite  account  of  a  disease  which  can 
be  identified  with  typhus  is  known  of  an  earlier  date 
than  the  eleventh  century.  It  was  not,  however,  until 
the  sixteenth  century  that  the  disease  was  described 
in  a  tolerably  satisfactory  manner  by  the  Italian 
physicians  (1505  to  1530).  Epidemics  of  typhus  have 
frequently  been  associated  with  the  devastations  of 
war  and  the  scarcity  of  food  resulting  from  such  de- 
vastations ;  or  from  failure  of  crops,  which  is  one  of 
the  principal  predisposing  causes  of  the  disease. 

During  the  eighteenth  century  the  disease  prevailed 
extensively  in  the  various  countries  of  Europe  and 
especially  in  England,  in  which  country  three  severe 
epidemics  occurred.  In  two  of  these  (1718-21  and 
i  728-31)  the  disease  was  widely  prevalent  in  England 

154 


TYPHUS  FEVER  155 

and  Scotland.  During  the  ten  years  following  1 734, 
and  again  in  1757  to  1775,  the  disease  prevailed  in 
the  track  of  contending  armies  over  a  large  part  of 
eastern  and  central  Europe.  The  last  mentioned 
period  includes  the  time  of  the  Seven  Years'  War, 
and  of  the  war  between  England  and  Spain.  At  the 
end  of  the  eighteenth  and  the  beginning  of  the  nine- 
teenth centuries  typhus  was  again  very  prevalent  in 
Europe.  Hirsch,  in  his  Handbook  of  Geographical 
and  Historical  Pathology,  says  with  reference  to  this 
period  : 

"  The  fourth  and  by  far  the  severest  period  of  typhus  in  the 
eighteenth  century  occupies  the  last  ten  years  of  it  ;  it  begins 
with  the  revolutionary  wars  on  French  soil,  and  ends,  in  the 
second  decade  of  the  present  century,  with  the  final  retreat  of 
the  French  army  across  the  Rhine,  the  overthrow  of  the  empire 
of  Napoleon,  and  the  restoration  of  peace." 

Widespread  epidemics  of  typhus  in  Europe  ceased 
with  the  ravages  attending  the  wars  of  Napoleon, 
with  the  exception  of  the  years  1846-47  when  the 
disease  was  somewhat  widely  diffused.  In  Ireland 
and  in  certain  other  parts  of  Europe  the  disease  is 
apparently  endemic,  and  any  unusual  period  of  distress 
is  apt  to  be  followed  by  an  epidemic.  In  America 
the  disease  has  prevailed  in  Mexico  from  an  early 
date  and  is  said  to  be  endemic  in  the  city  of  Mexico 
and  other  localities  in  the  interior.  It  has  also  been 


156  INFECTION  AND  IMMUNITY 

of  frequent  occurrence  in  Chili  and  in  Peru.  The 
disease  has  frequently  been  introduced  into  the 
United  States  by  immigrants  from  Europe,  and  local 
epidemics  have  resulted  from  such  importation,  es- 
pecially in  New  York  (1818,  1827,  1837,  1847)  and  in 
Philadelphia  (1827,  1835,  1847).  Fortunately  the 
disease  is  unknown  in  other  portions  of  the  United 
States,  probably  because  our  history  does  not  include 
any  famine  periods,  such  as  have  apparently  consti- 
tuted an  essential  factor  in  the  epidemic  prevalence 
of  the  disease  in  European  countries.  Africa  and 
Asia  have  been  to  a  great  extent  exempt  from  this 
scourge,  although  it  has  prevailed  in  northern  Africa, 
in  Persia,  and  in  Syria.  Typhus  is  essentially  a  dis- 
ease of  temperate  and  cold  countries.  In  the  popul- 
ous countries  and  islands  of  the  tropics  it  is  practically 
unknown.  Epidemics  occur  more  frequently  during 
the  winter  and  spring  months  than  in  summer.  This 
is  probably  due  to  the  fact  that  it  is  personally  con- 
tagious. Like  other  diseases  which  are  communicated 
from  person  to  person,  it  is  more  likely  to  extend 
when  cold  weather  leads  to  an  indoor  life  and  more 
intimate  and  continued  association  of  individuals. 
Again,  the  fact  that  scarcity  of  food  is  more  likely  to 
occur  in  winter  and  in  the  early  spring  is  probably  a 
factor  of  some  importance  in  determining  the  seasonal 
prevalence  of  the  disease. 


TYPHUS  FEVER  157 

The  influence  of  insanitary  conditions  in  favouring 
the  epidemic  extension  of  typhus  is  generally  admitted. 
This  is  so  well  stated  by  Hirsch  that  I  cannot  refrain 
from  again  quoting  from  this  trustworthy  author : 

"  It  is  always  and  everywhere  the  wretched  conditions  of  liv- 
ing, which  spring  from  poverty  and  are  fostered  by  ignorance, 
laziness,  helplessness,  in  which  typhus  takes  root  and  finds 
nourishment ;  and  it  is  above  all  in  want  of  cleanliness,  and  in  the 
overcrowding  of  dwellings,  that  are  ventilated  badly  or  not  at  all,  and 
are  tainted  with  corrupt  effluvia  of  every  kind.  The  prototype  of 
these  conditions  is  found  in  Ireland,  which  is  the  greatest  sufferer 
from  this  disease." 

The  same  conditions  as  to  overcrowding,  want  of 
ventilation,  and  insanitary  surroundings  have  been 
the  determining  factors  in  the  development  of  epi- 
demics in  prisons,  on  shipboard  ("  ship-fever "),  and 
among  colonies  of  workmen  brought  together  to  pro- 
secute great  engineering  enterprises  (canals,  railways, 
etc.),  and  not  provided  with  proper  quarters.  When 
poorly  housed  and  left  to  their  own  resources,  labourers 
or  soldiers  will  inevitably  develop  insanitary  conditions 
in  and  around  the  barracks,  huts,  or  tents  occupied  by 
them,  and  some  pestilential  malady  will  just  as  inevit- 
ably obtain  a  foothold  among  them,  with  more  or  less 
disastrous  consequences. 

The  germ  of  typhus  fever  has  not  been  discovered, 
but  it  is  an  eruptive  fever  in  which,  as  in  smallpox, 
the  infectious  agent  is  probably  given  off  from  the 


i58  INFECTION  AND  IMMUNITY 

entire  surface  of  the  body.  At  all  events  it  is  very 
contagious,  and  the  infection  clings  to  clothing  and 
other  articles  which  have  been  in  contact  with  the 
sick.  This  being  the  case,  our  chief  reliance  for  the 
prevention  of  the  disease  must  be  on  the  isolation  of 
the  sick,  and  careful  disinfection  of  all  articles  that 
have  been  exposed  to  infection  and  of  the  patient's 
body  and  excreta.  This  is  to  be  accomplished  by  the 
same  measures  recommended  in  the  case  of  smallpox. 

Owing  to  the  fact  that  typhus  fever  is  communi- 
cated by  personal  contact,  and  in  the  absence  of  any 
known  method  of  establishing  immunity  by  inocula- 
tion, physicians  and  nurses  are  especially  liable  to 
contract  the  disease.  During  the  epidemics  in  Ireland, 
between  the  years  1813  and  1848,  it  is  reported  that 
568  physicians  contracted  typhus  fever  and  of  these 
132  died.  During  the  Crimean  War,  the  mortality 
from  this  disease,  among  physicians  and  nurses,  was 
very  great. 

One  attack  of  typhus  usually  confers  immunity 
upon  the  individual,  but  second  attacks  may  occur. 
The  mortality  from  the  disease  is  slight  among  child- 
ren under  ten  years  of  age,  but  increases  with  age, 
being  highest  between  the  ages  of  thirty  and  fifty 

(41.97  #)• 


CHAPTER   VII 

TUBERCULOSIS 

TT  is  a  well-established  fact,  which  is  generally  re- 
cognised, that  pulmonary  consumption  is  due  to  a 
minute  bacillus,  discovered  over  twenty  years  ago  by 
the  famous  German  bacteriologist,  Robert  Koch,  and 
that  this  bacillus  is  present  in  large  numbers  in  the 
purulent  matter  coughed  up  from  the  lungs  of  those 
suffering  from  the  disease.  We  also  know  that  the 
propagation  of  the  disease  depends  largely  upon  the 
introduction  of  the  bacillus,  suspended  in  the  inspired 
air  in  the  form  of  dust,  to  the  lungs  of  susceptible 
individuals,  by  way  of  the  respiratory  passages.  That 
dust  in  hospitals  and  dwellings  occupied  by  consump- 
tive patients  may  contain  living  tubercle  bacilli  has 
been  repeatedly  demonstrated,  and  it  is  evident  that 
the  only  way  to  guard  against  this  danger  is  to 
destroy  by  fire  or  disinfecting  agents  all  expectorated 
material  coming  from  the  lungs  of  consumptive  pa- 
tients. If  this  is  done,  such  persons  do  not  endanger 
those  with  whom  they  are  associated  ;  if  it  is  not  done, 

159 


160  INFECTION  AND  IMMUNITY 

they  become  active  agents  in  the  transmission  of  this 
infectious  disease — "the  great  white  plague"-— which 
is  responsible  for  twelve  per  cent,  of  the  deaths 
which  occur  within  the  limits  of  the  United  States. 
The  last  census  report  shows  that  in  the  census 
year,  1900,  109,750  deaths  occurred  from  pulmonary 
consumption.  This  is  a  smaller  number  in  proportion 


FIG.  5.     Bacillus  of  tuberculosis,  as  seen  in  the  sputum  of  a  patient  having 
pulmonary  consumption  ;  magnified  1000  diameters. 

to  the  population  than  occurred  in  1890.  A  decided 
gain  is  shown  during  recent  years  by  the  mortality  sta- 
tistics of  some  of  our  large  cities,  in  which  special  ef- 
forts have  been  made  to  instruct  the  public  as  to  the 
method  in  which  the  disease  is  propagated,  to  prevent 
expectoration  in  public  places,  and  to  disinfect  the 
sputa  of  recognised  cases  of  pulmonary  tuberculosis. 
New  York  City,  under  the  able  leadership  of  Dr. 


TUBERCULOSIS  161 

Hermann  M.  Biggs,  Medical  Officer  of  the  Depart- 
ment of  Health,  has  taken  the  lead  in  carrying  out 
these  measures  for  the  prevention  of  the  disease, 
and  with  most  notable  results.  The  death-rate  from 
tuberculous  diseases  has  been  gradually  and  progress- 
ively reduced  from  4.42  per  cent,  in  1886  to  2.89  per 
cent,  in  1902.  Dr.  Biggs  says  in  a  recent  paper: 
"  During  the  first  six  months  of  1902,  4673  deaths 
from  tuberculosis  occurred,  equalling  a  reduction  of 
10  per  cent,  on  the  death-rate  of  1901,  which  was  the 
lowest  ever  recorded." 

As  to  the  methods  adopted  in  New  York,  Dr.  Biggs 
says : 

"In  1888  a  commencement  was  made  by  issuing  circulars  set- 
ting forth  the  essential  facts  regarding  the  nature  of  the  disease, 
the  usual  methods  of  its  transmission,  and  the  precautions  neces- 
sary to  prevent  its  spread.  Small  circulars  of  information  were  also 
freely  distributed  in  the  tenement-house  districts  and  the  public 
press  was  utilised  for  the  education  of  the  public  as  to  the  com- 
municable nature  of  tuberculosis.  This  campaign  of  education 
was  continued  until  1893  when  the  City  Board  of  health  required 
all  public  institutions  to  promptly  report  all  cases  of  pulmonary 
consumption  coming  under  observation  and  requested  physicians 
in  private  practice  to  do  the  same.  In  1897  a  section  was  added 
to  the  Sanitary  Code  declaring  pulmonary  tuberculosis  to  be  an 
*  infectious  and  communicable  disease,  dangerous  to  the  public 
health,'  and  requiring  physicians  to  report  to  the  Health  Depart- 
ment all  cases  coming  under  their  observation." 

Dr.  Biggs  concludes  his  paper,  from  which  I  have 
quoted,  as  follows  : 


162  INFECTION  AND  IMMUNITY 

"  It  seems  evident  that  sure  progress  is  being  made,  and  with 
the  cordial  support  of  the  medical  profession,  as  a  whole,  which  is 
now  freely  accorded  by  the  best  elements  of  the  profession,  fol- 
lowed as  this  must  be  by  the  universal  popular  appreciation  of 
the  true  nature  of  tuberculosis  in  place  of  the  unreasoning  fear 
or  careless  indifference  which  has  largely  prevailed,  we  may  con- 
'fidently  anticipate,  as  the  result  of  continued  effort,  the  almost 
entire  eradication  of  this,  the  most  fatal  disease  with  which  sani- 
tary authorities  have  to  deal." 

The  last  census  return  (1900)  shows  that  in  the 
registration  area  the  death-rate  from  consumption 
was  187.3  per  100,000  of  the  population,  while  the 
preceding  census  gave  a  rate  of  245.4  per  100,000. 

Similar  progress  is  reported  in  those  countries  of 
Europe  which  have  given  the  most  attention  to  sani- 
tary matters.  In  Prussia  a  notable  diminution  in  the 
mortality  from  tuberculosis  commenced  about  the 
year  1887,  five  years  after  the  discovery  of  the  tuber- 
cle bacillus.  This  has  been  continuous  up  to  the 
present  time.  Prior  to  the  date  mentioned,  the  mor- 
tality rate  from  tuberculosis  in  Prussia  had  for  some 
time  remained  stationary  at  about  310  per  100,000 
inhabitants;  since  the  year  1887,  it  has  fallen  to  210 
(in  the  year  1900).  Similar  progress  in  the  future 
would  lead  to  the  practical  extinction  of  the  disease 
in  twenty  or  thirty  years.  In  England,  during  the 
same  period,  a  reduction  from  240  to  190  per  100,000 
has  occurred.  The  last  census  return  shows  that  the 
District  of  Columbia  has  "  the  highest  death-rate 


TUBERCULOSIS  163 

(305.3)  from  consumption  in  the  registration  States." 
This  is  ascribed  to  the  large  proportion  of  coloured 
population. 

Recent  researches  have  led  Professor  Koch  to  the 
conviction  that  tuberculosis  is  more  often  communi- 
cated by  means  of  the  minute  drops  of  sputum 
forcibly  ejected  by  consumptive  patients  during  par- 
oxysms of  coughing  than  by  the  masses  of  sputum 
which  have  been  coughed  up  and  expectorated.  How- 
ever this  may  be,  there  can  be  no  doubt  that  the  main 
source  of  infection  is  to  be  found  in  the  sputum  of 
persons  suffering  from  pulmonary  tuberculosis.  In 
tuberculosis  of  the  bowels,  tubercular  meningitis,  and 
tubercular  joint  affections,  the  patient  must  have  been 
infected  by  such  material,  or  by  tubercle  bacilli  in  arti- 
cles of  food,  such  as  milk  or  meat  from  tuberculous 
animals.  But  such  cases  do  not  assist  in  propagating 
the  disease.  An  infant,  crawling  upon  the  floor  of 
an  infected  house,  is  especially  liable  to  infection 
through  the  medium  of  the  dust,  which  naturally  set- 
tles upon  the  floor,  and  to  develop  tubercular  menin- 
gitis, which  is  the  form  of  tubercular  infection  to 
which  young  children  are  most  subject.  Older  child- 
ren are  more  likely  to  contract  tubercular  joint 
disease — "  hip  disease,"  or  "  white  swelling  "  of  the 
knee  joint,"  or  tubercular  disease  of  the  spinal  col- 
umn ("  Pott's  disease  ").  The  child  with  tubercular 


164  INFECTION  AND  IMMUNITY 

meningitis  or  tubercular  peritonitis  is  usually  doomed 
to  death,  but  many  children  recover  from  the  other 
forms  of  tuberculosis  just  mentioned  and  may  grow 
up  to  be  useful  citizens,  although  the  results  of  the 
disease  from  which  they  suffered  are  manifest  in  the 
stiff  knee,  immovable  hip  joint,  or  deformed  spinal 
column. 

Susceptibility  to  pulmonary  tuberculosis  is  much 
greater  in  young  adults  than  in  children.  This  sus- 
ceptibility depends  upon  several  factors  which  consti- 
tute the  predisposing  causes.  First  we  may  mention 
an  inherited  weakness  of  constitution,  or  conforma- 
tion of  body — narrow  chest,  insufficient  lung  capacity, 
feeble  circulation,  imperfect  digestion.  Second  come 
the  conditions  relating  to  an  unfavourable  environ- 
ment— living  in  ill-ventilated  or  overheated  rooms, 
absence  of  sunlight  and  dampness  in  apartments 
occupied,  insanitary  surroundings,  overcrowding  of 
living-  and  sleeping-rooms.  Next  we  must  place 
lowered  vitality  as  a  result  of  other  acute  or  chronic 
diseases  or  of  vicious  habits,  and  the  catarrhal  inflam- 
mation of  the  bronchial  mucous  membrane  which  is  a 
prominent  feature  of  certain  other  infectious  diseases 
—especially  measles,  whooping-cough,  and  influenza 
—or  which  may  result  from  "  taking  cold."  Finally, 
occupation  has  much  to  do  with  establishing  a  predis- 
position to  the  disease. 


TUBERCULOSIS  165 

The  following  table,  compiled  from  the  last  census 
return  (1900),  gives  the  death-rate  per  100,000  from 
this  disease  for  persons  of  various  occupations  : 

Bankers,  brokers,  and  officials  of  companies 92 

Laundresses 94 

Farmers  and  farm  labourers 111.7 

Clergymen 1 23.5 

School-teachers,  female 126 

School-teachers,  male 144 

Railroad  employees 1 29.8 

Dressmakers  and  seamstresses 130 

Policemen 136.7 

Lawyers 139-9 

Mill  operators 144 

Physicians 158.8 

Gardeners  and  florists ...    186.6 

Journalists 1 88.4 

Carpenters 231 

Masons 293 

Book-keepers  and  clerks 308 

Painters  and  glaziers 319 

Servants,  female 319.7 

Sailors  and  fishermen 333 

Barbers 334.9 

Cabinet-makers 359 

Labourers 370 

Servants,  male 430 

Printers 435-9 

Cigar-makers 476 

Marble-  and  stone-cutters 540 

Occupations  in  which  the  air  is  filled  with  dust  par- 
ticles, which  irritate  the  bronchial  mucous  membrane, 


1 66  INFECTION  AND  IMMUNITY 

and  are  often  deposited  in  the  lungs  in  considerable 
quantities,  constitute  a  predisposition  to  infection,  as 
is  shown  by  the  high  death-rate  among  marble-  and 
stone-cutters. 

The  number  of  deaths  from  consumption  both  in 
this  country  and  in  England  is  greater  among  males 
than  among  females.  In  the  United  States,  the  total 
number  of  deaths  from  this  disease,  reported  as  occur- 
ring in  the  registration  area  during  the  last  census 
year,  was  53,962,  of  which  29,192  were  males  and 
24,770  females. 

The  Imperial  Health  Board  of  Berlin  has  issued 
the  following  statistics  regarding  the  mortality  from 
phthisis  in  Europe :  Russia  has  more  than  4000 
deaths  per  1,000,000;  Austria-Hungary  and  France, 
more  than  3000  per  1,000,000;  Sweden,  Germany, 
Switzerland,  and  Ireland,  more  than  2000  per  1,000,- 
ooo ;  Netherlands,  Italy,  Belgium,  Norway,  Scotland, 
and  England,  more  than  1000  deaths  per  1,000,000. 

Certain  races  seem  to  be  especially  liable  to  infec- 
tion by  the  tubercle  bacillus.  The  census  return  (1900) 
shows  that  among  those  whose  mothers  were  born  in 
Ireland  the  rate  was  339.6  per  100,000,  in  France 
184.7,  m  Scotland  172.5,  in  the  United  States  112.8, 
in  Russiaand  Poland  71.8.  The  comparative  immun- 
ity of  Russian  and  Polish  Jews  from  pulmonary  con- 
sumption had  previously  been  established  by  the  vital 


TUBERCULOSIS  167 

statistics  of  the  city  of  New  York  for  the  six  years 
ending  in  1890.  It  was  found  to  be  76.72  per  100,- 
cxx),  while  for  Irish,  during  the  same  period,  it  was 
645.73,  for  coloured  531.35,  for  Germans  328.8,  and 
for  native-born  Americans  205.14.  With  reference 
to  age,  the  statistics  show  a  comparatively  low  rate 
below  the  age  of  fifteen,  a  rate  of  252.4  between  fif- 
teen and  forty-four,  a  smaller  rate  between  forty-five 
and  sixty-four  years  of  age  (232.5),  and  a  maximum 
rate  of  260.1  beyond  the  age  of  sixty-five. 

While  pulmonary  consumption  is  an  extremely  fatal 
disease  when  those  who  contract  it  are  obliged  to 
live  under  the  unfavourable  conditions  which  con- 
tributed to  its  development,  it  is  now  well  known  that 
cases  in  the  early  stages  of  the  disease  are  very 
amenable  to  suitable  treatment,  and  that  a  consider- 
able proportion  of  the  cases  recover  under  the  influ- 
ence of  pure  air  and  nourishing  food.  The  fact  that 
there  is  no  specific  medication  for  the  disease  is  set 
forth  in  the  following  authoritative  circular. 

"THE  COMMITTEE  ON  THE  PREVENTION  OF  TUBERCU- 
LOSIS OF  THE  CHARITY  ORGANISATION  SOCIETY 
OF  THE  CITY  OF  NEW  YORK 

"WHEREAS,  It  has  come  to  the  knowledge  of  the  Committee 
on  Tuberculosis  of  the  Chanty  Organisation  Society  that  many 
so-called  specific  medicines  and  special  methods  of  cure  for 
tuberculosis  have  been  and  are  being  exploited  and  widely 
advertised,  and 


i68 


INFECTION  AND  IMMUNITY 


"  WHEREAS,  The  advertisements  of  some  of  these  cures  have 
made  such  reference  to  the  Tuberculosis  Committee  of  the  Char- 
ity Organisation  Society,  or  to  some  of  its  members,  as  to  create 
the  inference  that  this  Committee,  or  its  members,  recommend 
or  advocate  the  use  of  many  such  so-called  specifics  or  special 
methods  of  cure  for  pulmonary  tuberculosis,  or  consumption, 
and 

"  WHEREAS,  There  is  no  specific  medicine  for  this  disease 
known,  and  the  so-called  cures  and  specifics  and  special  methods 
of  treatment  widely  advertised  in  the  daily  papers  are  in  the 
opinion  of  the  Committee  without  special  value,  and  do  not  at 
all  justify  the  extravagant  claims  made  for  them,  and  serve 
chiefly  to  enrich  the  promoters  at  the  expense  of  the  poor  and 
frequently  ignorant  or  credulous  consumptives,  therefore, 

"  RESOLVED,  That  a  public  announcement  be  made  that  it  is  the 
unanimous  opinion  of  the  members  of  this  Committee  that  there 
exists  no  specific  medicine  for  the  treatment  of  pulmonary  tuber- 
culosis, and  that  no  cure  can  be  expected  from  any  kind  of 
medicine  or  method  except  the  regularly  accepted  treatment 
which  relies  mainly  upon  pure  air  and  nourishing  food. 


CHARLES  F.  Cox,  Chairman 
OTTO  T.  BANNARD 
HERMANN  M.  BIGGS,  M.D. 
HERBERT  S.  BROWN 
JOSEPH  D.  BRYANT,  M.D. 
Miss  ELLA  MABKL  CLARK 
ROBERT  W.  DE  FOREST 
EDWARD  T.  DEVINE 
HOMER  FOLKS 
FRANKLIN  H.  GIDDINGS 
HENRY  HERBERT,  M.D. 
J.  H.  HUDDLESTON,  M.D. 
ROBERT  HUNTER 
A.  JACOBI,  M.D. 
WALTER  B.  JAMES,  M.D. 
E.  G.  J  ANEW  AY,  M.D. 

CHARLES  H.  JOHNSON,  Secretary. 
105  East  22d  Street." 


Miss  A.  B.  JENNINGS 

S.  A.  KNOPE,  M.D. 

ALEXANDER  LAMBERT,  M.D. 

ERNEST  J.  LEDERLE 

Mrs.  FREDERIC  S.  LEE 

EGBERT  LE  FEVRE,  M.D. 

HENRY  P.  LOOMIS,  M.D. 

Mrs.  JAMF.S  E.  NEWCOMB 

EUGENE  A.  PHILBIN 

T.  MITCHELL  PRUDDEN,  M.D. 

ANDREW  H.  SMITH,  M.D. 

W.  G.  THOMPSON,  M.D. 

E.  L.  TRUDEAU,  M.D. 

FREDERICK  L.  WACHENHEIM,  M.D. 

R.  C.  W.  WADSWORTH 

Miss  LILLIAN  D.  WALD 


TUBERCULOSIS  169 

No  doubt  the  favourable  results  as  regards  a  dim- 
inution in  the  mortality  from  consumption,  which 
have  been  obtained  in  England,  Germany,  and  cer- 
tain portions  of  the  United  States,  are  due  in  part  to 
improved  housing  conditions  among  the  poor,  and  in 
part  to  the  removal  of  consumptive  patients  to  sana- 
toria, rather  than  to  the  disinfection  of  sputa,  which  is 
still  very  imperfectly  carried  out. 

The  treatment  of  cases  of  pulmonary  tuberculosis  in 
special  hospitals  or  sanatoria  has  a  twofold  advantage. 
It  is  in  the  interest  both  of  the  patients  and  of  the 
general  public.  It  has  been  demonstrated  that  under 
proper  treatment  in  well-located  sanatoria  a  consider- 
able proportion  of  the  cases  may  recover,  and  that 
the  methods  adopted  in  such  sanatoria  for  the  de- 
struction of  the  sputa  of  tuberculous  patients  prevents 
the  infection  of  the  buildings  and  grounds. 

On  the  other  hand,  private  dwellings,  especially 
among  the  poorer  classes  of  the  "community,  are  al- 
most sure  to  become  infected  by  the  prolonged  resid- 
ence in  them  of  a  case  of  pulmonary  consumption, 
and  sad  experience  shows  that  a  first  case  is  often 
followed  by  a  series  of  cases,  which,  occurring  in  one 
family,  were  formerly  ascribed  to  heredity.  The  per- 
sistent infection  of  localities  in  which  cases  have 
occurred  is  illustrated  in  the  vital  statistics  of  every 
city.  Thus  in  New  York  City  "  on  a  single  street 


1 7o  INFECTION  AND  IMMUNITY 

block  as  many  as  102  cases  have  been  reported 
within  a  period  of  4f  years  and  as  many  as  24 
cases  in  a  single  house."  If  we  were  speaking 
of  bubonic  plague  and  the  same  number  of  cases  had 
occurred  within  the  same  period,  the  whole  country 
would  be  alarmed  and  the  most  rigorous  efforts 
would  be  made  to  eradicate  the  disease,  but  "the 
great  white  plague "  continues  to  claim  its  annual 
quota  of  from  110,000  to  150,000  victims  within  the 
limits  of  the  United  States,  and  the  known  measures 
of  prevention  are  either  entirely  neglected  or  carried 
out  in  a  very  inadequate  manner  in  a  large  portion  of 
our  great  and  prosperous  country. 

For  the  prevention  of  tuberculosis,  as  already  in- 
dicated, the  most  essential  sanitary  measure  is  the 
destruction  of  the  tubercle  bacillus  in  the  sputa  of 
those  suffering  from  pulmonary  consumption.  This 
may  readily  be  effected  when  the  victims  of  the  dis- 
ease and  those  associated  with  them  become  con- 
vinced of  its  importance.  For  this  reason  well-informed 
physicians  and  sanitary  officials  consider  the  education 
of  the  public  a  matter  of  prime  necessity.  It  is  hardly 
necessary  to  say  that  the  sputa  of  tuberculous  pa- 
tients should  be  deposited  in  some  suitable  vessel 
and  never  upon  the  floor  or  ground.  Regulations 
prohibiting  expectoration  upon  the  sidewalks  or 
upon  the  floor  in  public  vehicles,  etc.,  have  been 


TUBERCULOSIS  171 

adopted  in  several  cities  in  the  United  States  and 
should  be  enforced  everywhere,  not  only  in  the  inter- 
est of  the  public  health  but  as  a  matter  of  decency. 
There  was  a  time  when  all  kinds  of  filth  could  be 
thrown  into  the  streets  of  cities  without  danger  of 
police  interference.  But  the  public  has  long  since 
been  educated  beyond  the  point  of  submitting  to 
such  nuisances,  and  the  time  is  not  far  distant  when 
no  self-respecting  citizen  will  deposit  masses  or  pools 
of  expectorated  matter  in  public  places  any  more 
than  he  would  upon  the  floor  of  his  own  drawing- 
room.  Those  who  have  no  self-respect  or  regard  for 
the  sensibilities  of  their  neighbours  should  be  re- 
strained by  suitable  laws. 

When  infected  saliva  has  been  deposited  in  a  suit- 
able receptacle  of  porcelain  or  of  metal  it  is  a  simple 
matter  to  destroy  it.  This  may  be  readily  accom- 
plished by  placing  the  receptacles  with  their  contents 
in  boiling  water  for  at  least  five  minutes.  A  five- 
per-cent.  solution  of  carbolic  acid  or  one  of  the  other 
coal-tar  disinfectants  (lysol,  creolin,  tricresol)  may  be 
used  for  the  same  purpose,  and  it  is  a  good  plan 
to  have  the  sputum  directly  deposited  in  a  porcelain 
cuspidor  containing  such  a  solution.  This  should  be 
emptied  and  cleaned  in  boiling  water  at  least  twice  a 
day.  Various  forms  of  cuspidors  have  been  devised 
for  tuberculous  patients  and  are  to  be  obtained  from 


1 7  2  INFECTION  AND  I  MM  UNI  TY 

dealers  in  medical  and  surgical  appliances.  Those 
which  are  made  of  enamelled  iron,  tin,  or  aluminum 
have  the  advantage  of  not  being  breakable.  They 
should  be  provided  with  a  cover  to  exclude  flies  and 
hide  the  contents  from  view.  Pasteboard  cups, 
which  can  be  placed  inside  of  a  metal  cup  with  cover, 
are  especially  to  be  commended  as  they  can  be  re- 
moved and  burned,  together  with  their  contents,  at 
stated  intervals. 

Pocket  flasks  of  aluminum  are  made  for  the  use  of 
tuberculous  individuals  who  are  not  confined  to  the 
house.  Dr.  Knopf,  of  New  York,  in  his  valuable  ar- 
ticle in  the  Twentieth  Century  Practice  of  Medicine, 
makes  the  following  remarks  with  reference  to  pocket 
flasks : 


"  The  pocket  flask, when  properly  and  faithfully  used  by  the  pul- 
monary invalid,  will  prove  one  of  the  most  important  factors  in 
the  prevention  of  tuberculosis.  It  should  be  carried  by  the  tuber- 
culous individual  all  the  time  and  used  whenever  he  cannot 
conveniently  get  at  the  stationary  cuspidors.  The  first  pocket 
spittoon  was  Dr.  Dettweiler's  '  Hiistenflaschen.'  It  is  a  flask  of 
blue  glass  about  four  inches  long  and  six  inches  in  its  largest 
circumference,  provided  with  a  hermetically  closing  top  and 
bottom  of  white  metal,  and  so  constructed  that  it  can  easily  be 
cleaned.  The  lid  flies  open  at  a  slight  pressure  on  the  spring, 
and  after  use  is  closed  by  pushing  the  top  down  again.  Since 
the  appearance  of  this  flask  many  similar  utensils  have  been 
devised,  partly  with  a  view  of  simplifying  the  mechanism  and  also 
of  producing  an  article  cheap  enough  to  be  within  the  reach  of 
every  one. 


TUBERCULOSIS  173 

"  In  the  endeavour  to  attain  these  ends  I  have  designed  two 
models.  The  better  of  these,  perhaps,  is  the  aluminum  flask  con- 
structed like  Dettweiler's,  but  without  the  extra  opening  at  the 
bottom. 

"  It  is  lighter,  less  bulky,  and  unbreakable.  It  is  easy  to  disin- 
fect as  it  can  be  boiled  without  injury.  It  possesses  every  ad- 
vantage except  that  of  cheapness.  The  other  is  a  strong  glass 
flask  modelled  like  the  aluminum  flask  just  described.  The  fun- 
nel is  of  vulcanised  rubber  and  the  cover  of  white  metal.  The 
cleaning  and  disinfection  are  simple,  and  its  cost  is  only  about 
one-third  of  that  of  the  aluminum  flask.  .  .  .  All  of  these  flasks 
are  so  constructed  that  the  contents  cannot  be  spilled  when 
tipped  over,  even  when  the  cover  is  open.  .  .  .  The  patient 
should  have  two  pocket  flasks,  so  as  never  to  be  without  while  one 
is  being  cleaned." 

The  reporting  of  cases  of  pulmonary  tuberculosis, 
by  their  attending  physicians,  to  the  health  authorities, 
should  be  required,  not  with  a  view  to  isolation  of  the 
patient,  as  is  demanded  in  the  case  of  acute  infectious 
diseases,  but  in  order  that  the  patient  and  his  friends 
may  receive  reliable  information  with  reference  to  the 
danger  of  the  transmission  of  the  disease  and  the 
method  of  preventing  it.  In  New  York  City,  which 
has  taken  the  lead  in  this  country  in  preventive  meas- 
ures, the  method  of  procedure  is  stated  by  Dr.  Her- 
mann M.  Biggs,  Medical  Officer  of  the  Health 
Department,  as  follows  : 

"  With  certain  exceptions,  such  as  patients  under  the  care 
of  private  physicians,  all  reported  cases,  living  or  dead,  are 
assigned  to  the  medical  inspectors  of  tuberculosis  for  the  district 


174  INFECTION  AND  IMMUNITY 

from  which  the  cases  are  reported.  The  inspector  visits  the  ad- 
dress given,  and,  if  the  patient  is  living,  leaves  a  circular  of  in- 
formation and  gives  verbal  instruction  to  the  friends  about  the 
danger  of  infection  and  the  care  of  the  sputum.  If  the  address 
is  that  of  a  dead  patient,  or  if  the  patient,  though  living,  has 
moved,  the  inspector  examines  the  premises  and  makes  such  re- 
commendations as  seem  to  him  necessary  to  render  the  habita- 
tion free  from  danger  of  infection.  These  recommendations, 
made  out  on  a  prescribed  form,  usually  advise  the  following 
routine  treatment  of  apartments:  Kalsomined  or  whitewashed 
walls  or  ceilings  are  washed  with  a  solution  of  washing  soda  (one- 
half  pound  to  three  gallons  of  hot  water),  and  then  kalsomined 
or  whitewashed  again;  papered  walls  or  ceilings  are  similarly 
washed  and  repapered;  the  woodwork  is  scrubbed  with  the  soda 
solution  and  repainted.  The  inspector's  recommendations  are 
forwarded  to  the  board,  and  on  them  as  a  basis  a  ten-day  order 
is  issued  on  the  landlord  requiring  him  to  carry  out  the  specified 
renovation.  The  execution  of  the  order  is  then  (as  with  all 
others  of  the  board)  placed  under  the  supervision  of  the  sanitary 
police.  The  premises  are  reinspected,  and  if,  at  the  expiration 
of  ten  days,  the  owner  has  not  complied  with  the  order,  it  is  re- 
ferred to  the  attorney  of  the  board  for  enforcement.  This  pro- 
cedure was  determined  on  because  of  the  difficulty  of  disinfection 
of  apartments  in  which  cases  of  tuberculosis  have  been,  and  the 
greater  efficiency  attained  by  the  system  of  renovation.  The 
method  is  easy  of  enforcement,  as  is  shown  by  the  fact  that  com- 
pliance with  the  order  has  not  been  refused  in  a  single  case. 
The  chief  point  of  interest  in  this  plan  is  that  renovation  rather 
than  disinfection  is  called  for.  Disinfection  involves  the  use  of 
materials  and  methods  which  are  not  universally  familiar.  The 
method  of  renovation  required  is  understood  by  all,  and  is 
more  efficient  than  any  method  of  disinfection  which  could 
be  employed." 

Prior  to  this  renovation   the    room    with  its  con- 
tents may  be  disinfected  with    formaldehyd  gas,   or 


TUBERCULOSIS  175 

articles  of  clothing  and  bedding  which  cannot  be  sent 
to  the  laundry  may  be  disinfected  by  the  Health  De- 
partment, at  its  disinfecting  station,  either  by  steam 
or  formaldehyd. 

The  danger  of  contracting  tuberculosis  through 
the  medium  of  milk  from  tuberculous  cows  is  to  be 
guarded  against  by  the  killing  of  animals  recognised 
as  tuberculous  and  by  the  sterilisation  of  milk  when 
it  comes  from  a  source  not  known  to  be  free  from 
suspicion. 

That  the  tubercle  bacillus  is  frequently,  if  not 
usually,  present  in  the  milk  of  tuberculous  cows,  has 
been  demonstrated  by  numerous  independent  investi- 
gators. 

We  regard  the  danger  of  contracting  the  disease 
by  eating  the  flesh  of  tuberculous  animals  as  ex- 
tremely remote.  This  should  be  condemned  if  the 
animal  is  found  to  have  the  lesions  of  pulmonary 
tuberculosis  ;  but  if  these  are  not  discovered,  the  facts 
that  the  bacilli  are  not  located  in  the  muscles,  and 
that  the  meat  is  cooked  before  it  is  eaten,  probably 
reduce  the  danger  to  an  imaginary  one. 

It  has  been  shown  by  experiment  that  tubercle 
bacilli  may  retain  their  vitality  and  infecting  power 
in  desiccated  sputum  for  several  months.  Infected 
houses  are  therefore  dangerous  for  a  considerable 
time  after  they  have  been  vacated  by  a  consumptive 


i76  INFECTION  AND  IMMUNITY 

person.  The  bacillus  may  also  retain  its  vitality  for 
one  hundred  days  or  more  in  putrefying  material. 
This  bacillus  has  also  greater  resistance  to  heat  and 
various  germicidal  agents  than  most  other  pathogenic 
bacteria.  But  it  is  quickly  killed  by  exposure  to  the 
temperature  of  boiling  water  ;  by  a  five-per-cent.  solu- 
tion of  carbolic  acid  ;  by  a  two-per-cent.  solution  of 
chloride  of  lime  ;  by  milk  of  lime,  solution  of  caustic 
potash  (lye),  or  the  mineral  acids  —  a  one-per-cent. 
solution  of  sulphuric  or  hydrochloric  acid.  Wood 
vinegar,  or  pyroligneous  acid  may  also  be  used  if  at 
least  six  hours'  time  is  allowed  for  disinfection. 

What  has  been  said  with  reference  to  predisposing 
causes  will  indicate  the  measures  which  should  be 
taken  to  increase  the  resistance  of  individuals  to  in- 
fection— especially  of  those  who  have  an  inherited  or 
acquired  feebleness  of  constitution.  An  out-door  life, 
systematic  exercise,  and  a  nutritious  diet  will  be  the 
main  factors  in  establishing  a  relative  immunity  to 
the  disease.  Children  with  narrow  chests  and  insuf- 
ficient lung  capacity  should  be  required  to  take  breath- 
ing exercises  as  prescribed  by  Dr.  Knopf,  of  New 
York. 


"  The  patient  is  taught  to  stand  properly — that  is  to  say, 
straight,  chest  out,  and  head  erect — and  to  breathe  always  through 
the  nose.  He  takes  a  deep  inspiration  slowly,  beginning  with  the 
abdominal  muscles,  and  then  expanding  the  chest  to  its  fullest 


TUBERCULOSIS  177 

capacity.  During  this  inspiration  he  raises  his  arms  from  his 
sides  to  a  horizontal  position.  He  holds  the  breath  for  a  moment 
and  then  lowers  the  arms  during  the  act  of  expiration,  which 
should  be  somewhat  more  rapid. 

"  The  second  exercise  is  like  the  first,  except  that  the  upward 
movement  of  the  arms  is  continued  until  the  hands  meet  over 
the  head. 

"  In  the  third  exercise  the  patient  stretches  his  arms  out  as  in 
the  position  of  swimming,  the  backs  of  the  hands  touching  each 
other.  During  the  inspiration  the  arms  are  moved  outwards  and 
finally  meet  behind  the  back.  They  are  brought  forward  again 
during  the  expiration.  This  exercise  can  be  greatly  facilitated 
and  made  more  effective  by  the  patient  rising  on  his  toes  during 
the  act  of  inspiration  and  descending  during  the  act  of  expira- 
tion. Each  respiratory  act  should  be  followed  immediately  by 
a  secondary  forced  expiratory  effort." 


Exercises  of  this  kind  should  not  be  taken  soon 
after  eating  or  when  greatly  fatigued.  Abundant 
ventilation  of  sleeping-  and  living-rooms  and  sun-baths 
will  do  much  to  invigorate  the  system.  When  practi- 
cable, delicate  children  and  individuals  already  infected 
by  the  tubercle  bacillus  should  have  the  advantage  of  a 
favourable  climate,  such  as  that  of  portions  of  Colo- 
rado, New  Mexico,  or  Arizona,  where  one  may  be 
out-of-doors  nearly  every  day  in  the  year,  and  where 
the  continued  sunshine  and  pure  invigorating  air  often 
work  wonders  in  the  way  of  re-establishing  the  health 
of  such  persons. 

To  further  enforce  the  statements  made  in  this 
chapter,  I  take  the  liberty  of  quoting  from  a  recently 


i y8  INFECTION  AND  IMMUNITY 

published  paper  by  Dr.  Hermann  M.  Biggs,  Medical 
Officer  of  the  Department  of  Health  of  New  York 
City: 

"  Last  year  there  were  reported  to  the  Department  of  Health 
more  than  13,000  new  cases.  It  may  be  safely  estimated  that 
this  represents  less  than  one-half  of  the  cases  actually  existing  in 
New  York  City,  for  many  cases  live  for  several  years  after  they 
are  brought  to  the  attention  of  the  Department,  and  are  only  in- 
cluded when  originally  reported,  and  many  are  not  reported  at 
all.  For  example,  nearly  5000  other  cases  were  reported  in  1901, 
which  had  been  previously  reported.  I  think  we  may  safely  esti- 
mate that  30,000  cases  of  tuberculosis  in  a  stage  of  the  disease  in 
which  it  could  be  easily  recognised  by  a  competent  physician 
are  present  in  New  York  City. 

44 1  have  had  a  census  of  the  cases  actually  under  treatment  in 
the  hospitals  in  New  York  City  made  annually  for  a  series  of 
years,  and  the  total  number  never  much  exceeded  1000,  or  less 
than  4  per  cent,  of  the  cases  actually  present  in  'the  city.  The 
vast  proportion  of  the  remainder  are  in  tenement  houses.  I 
have  estimated  that  the  total  expenditure  in  the  city  of  New 
York  in  its  public  institutions  for  the  care  and  treatment  of  tu- 
berculous patients  is  not  over  $500,000  a  year,  or  not  more  than  2 
per  cent,  of  the  actual  loss  to  the  city  annually.  If  this  annual 
expenditure  were  doubled  or  trebled  it  would  mean  a  saving  of 
several  thousand  lives  annually,  to  say  nothing  of  the  enormous 
saving  in  suffering. 

"  It  is  now  fifteen  years  since  the  New  York  City  Health  De- 
partment first  began,  in  a  very  small  way,  its  efforts  for  the  pre- 
vention of  tuberculosis,  and  these  have  been  rewarded  by  a 
reduction  in  the  mortality  out  of  all  proportion  to  the  expendi- 
ture in  money  and  time  which  has  been  made.  Still,  more  has 
been  done  in  New  York  than  in  almost  any  city  in  the  world. 
The  measures,  however,  now  in  force  are  quite  inadequate,  as 
compared  with  the  importance  and  magnitude  of  the  problem. 
The  sanitary  authorities,  however  enthusiastic  and  efficient,  and 


TUBERCULOSIS  179 

the  medical  profession,  however  influential  and  numerous,  can- 
not grapple  with  this  problem  unless  they  have  the  hearty  support 
of  the  people  and  the  administration  of  the  city.  They  must 
have  generous  appropriations  for  carrying  on  the  work  —  for  the 
provision  of  medical  inspectors  and  disinfectors,  for  educational 
measures,  for  the  establishment  of  dispensaries  and  sanatoria  for 
the  care  of  incipient  cases,  and  of  homes  to  which  advanced 
cases  may  be  removed,  and  where  they  may  be  made  comfortable 
until  the  inevitable  fatal  termination  comes.  We  must  remem- 
ber, in  this  connection,  that  every  incipient  case  and  every  ad- 
vanced case  of  tuberculosis  which  is  removed  from  its  home  and 
surroundings  and  placed  in  a  properly  equipped  and  conducted 
institution  is,  in  this  way,  not  only  given  a  fair  chance  for  recovery 
of  health,  but  is  educated  as  to  the  means  to  be  taken  to  prevent 
further  extension  of  infection,  and,  at  the  same  time,  one  focus  of 
infection  is  removed  from  the  city.  On  the  average,  every  case  of 
tuberculosis  infects  at  feast  one  other  case,  and  if  removed  to  a 
hospital  early  enough,  the  infection  of  this  second  case  would  be, 
in  each  instance,  prevented,  and  thus  the  total  number  of  cases 
would  be  reduced. 

"  It  is  in  an  educational  way  that  lay  organisations  for  the  pre- 
vention of  tuberculosis  may  be  of  the  greatest  service.  They 
serve  to  arouse  interest  in  and  to  disseminate  knowledge  of  the 
nature  of  tuberculosis;  they  form  compact  bodies  of  public-spir- 
ited citizens,  whose  influence  is  of  the  greatest  value  in  so  mould- 
ing public  sentiment  that  funds  shall  be  forthcoming  to  erect 
and  maintain  dispensaries,  sanatoria,  and  homes  for  the  consump- 
tive poor.  Through  their  assistance,  and  that  of  the  public  press, 
we  may  hope  eventually  to  obtain  State  and  municipal  appropria- 
tions for  the  suitable  care  of  the  consumptive  poor.  New  York 
State  has  made  a  small  beginning  in  this  way,  and  it  is  hoped 
that  the  State  sanatorium,  now  in  course  of  erection  in  the  Adi- 
rondacks,  may  lead  to  very  much  larger  appropriations  for  this 
purpose.  The  State  is  spending  many  millions  of  dollars  annu- 
ally for  the  care  of  the  insane,  and  while  this  is  absolutely  neces- 
sary, for  humanitarian  reasons,  I  have  no  hesitation  in  saying 
that  far  greater  returns  would  be  obtained  from  the  expenditure 


i8o  INFECTION  AND  IMMUNITY 

of  one-quarter  the  amount  in  the  prevention  and  cure  of  tuber- 
cular disease. 

"I  believe  that  tuberculosis  may  be  practically  stamped  out. 
The  reduction  in  the  mortality  from  it  in  New  York  City,  since 
1886,  has  been  about  40  per  cent.,  which  means  if  applied  to  the 
Greater  City,  a  decrease  of  more  than  6000  in  the  number  of 
deaths  annually  caused  by  it.  The  vast  significance  of  this  is 
still  more  enhanced  when  we  remember  that  to  a  very  large  ex- 
tent these  deaths  take  place  in  the  working  period,  between  fifteen 
and  fifty-five  years  of  age.  I  have  no  doubt  that  the  measures, 
first  begun  in  a  very  small  way  in  New  York  City  fifteen  years 
ago,  inadequate  as  they  have  been,  have  resulted  in  saving  the 
lives  of  at  least  twenty  thousand  persons.  The  annual  deaths  in 
the  Greater  City  still  number  between  nine  and  ten  thousand, 
and  we  know  that  these  are,  to  a  very  large  extent,  unnecessary." 


CHAPTER   VIII 
LEPROSY 

T  E  PROSY  is  an  infectious  disease  due  to  a  bacillus, 
^  discovered  in  1879  by  Hansen,  a  Norwegian 
physician.  This  bacillus  is  found  in  great  numbers 
in  the  cells  contained  in  the  leprous  nodules,  which 
are  characteristic  of  the  disease.  In  its  form  the  lep- 
rosy bacillus  resembles  the  tubercle  bacillus,  but  bac- 
teriologists have  failed  in  their  attempts  to  cultivate 
it  in  artificial  media  and  in  communicating  the  disease 
to  lower  animals,  as  has  been  repeatedly  done  in  the 
case  of  the  tubercle  bacillus.  Nor  has  it  been  de- 
termined in  a  definite  manner  how  the  disease  is  con- 
tracted. It  is  not,  unless  in  very  exceptional  cases, 
communicated  by  the  sick  to  those  in  close  associa- 
tion with  them.  Thus  among  the  Sisters  of  Charity 
who  have  for  many  years  taken  care  of  the  sick  in 
the  lepers'  hospital  at  Havana,  not  one  has  ever 
contracted  the  disease.  Inoculation  experiments  in 
healthy  men,  made  with  the  knowledge  and  consent 

181 


1 82  INFECTION  AND  IMMUNITY 

of  those  inoculated,  have  been  repeatedly  made  by 
investigators  with  a  negative  result.  In  these  in- 
oculations, blood,  pus,  and  portions  of  the  leprous 
tissues  containing  numerous  bacilli  have  been  used. 
In  a  single  instance  only  was  such  an  inoculation 
followed  by  the  development  of  leprosy,  but  this 
man  belonged  to  a  leprous  family  and  it  is  not  cer- 


FIG.  6.     Bacillus  of  leprosy,  as  seen  in  a  thin  section  of  a  leprous  nodule  ; 
magnified  1000  diameters. 

tain  that  the  disease  in  his  case  was  a  result  of  the 
inoculation. 

The  question  as  to  whether  leprosy  is  contagious 
has  been  much  discussed  by  physicians,  and  while 
this  has  been  most  positively  denied  by  many  phy- 
sicians, and  certainly  does  not  occur  under  ordinary 
conditions,  the  opinion  seems  to  be  gaining  ground 


LEPROSY  183 

that  in  some  way  it  must  be  communicated  from  the 
sick  to  the  well.  Indeed,  it  would  otherwise  be  diffi- 
cult to  conceive  as  to  how  the  disease  is  propagated. 
Certain  families  manifest  a  special  susceptibility  to 
the  disease  and  its  hereditary  transmission  is  claimed 
by  some  authorities  ;  but  if  we  admit  this  it  will  not 
account  for  the  development  of  the  disease  in  pre- 
viously healthy  adults  and  in  the  cases  occurring  in 
individuals  whose  parents  had  no  taint  of  the  disease. 
Moreover,  there  are  numerous  instances  of  individuals 
born  of  leprous  parents  who  have  grown  to  manhood 
or  womanhood  without  developing  the  disease.  The 
intimate  association  of  husband  and  wife,  also,  fails 
in  most  instances  to  give  rise  to  leprosy  in  the  healthy 
member  of  the  pair,  the  other  being  a  leper. 

Notwithstanding  the  facts  stated  most  recent  au- 
thorities insist  that  leprosy  is  a  contagious  disease 
which  can  be  communicated,  under  conditions  not  yet 
well  understood,  by  those  infected  with  the  bacillus 
of  the  disease  to  healthy  individuals  having  a  special 
predisposition  to  such  infection.  According  to  Dr. 
Morrow  of  New  York,  who  has  made  a  special  study 
of  this  disease  :  "  The  literature  of  leprosy  abounds 
with  well-authenticated  cases  of  individual  contagion, 
showing  in  the  clearest  and  most  positive  manner 
that  the  disease  spreads  from  leprous  to  healthy  per- 
sons by  contact."  The  same  author  says  : 


i84  INFECTION  AND  IMMUNITY 

"  If  the  observer  limits  his  field  of  examination  and  judgment 
to  certain  parts  of  Europe  and  the  United  States,  he  may  find 
little  clinical  evidence  of  the  active  spread  of  leprosy  by  con- 
tagion. Observation  shows  that  leprous  germs  introduced  into 
these  favoured  regions  do  not  take  root  and  spread;  they  rarely 
survive  the  death  of  the  leper.  In  New  York,  for  example,  large 
numbers  of  lepers  coming  from  countries  where  leprosy  is  en- 
demic have  lived  for  years,  many  of  them  have  been  sent  to  gen- 
eral hospitals,  where  they  have  died,  and  yet,  so  far  as  is  known, 
no  case  of  indigenous  leprosy  can  be  traced  to  association  or 
contact  with  these  patients.  The  same  experience  has  been 
noted  in  London,  Paris,  and  Berlin,  where  lepers  from  other 
countries  have  flocked  for  treatment  and  have  been  received  in 
the  general  hospitals  without  special  measures  of  isolation,  and 
yet  no  case  of  leprous  contamination  has  been  traced  to  contact 
with  them." 


The  same  author  calls  attention  to  the  fact  that 
one  hundred  and  sixty  Norwegian  leper  immigrants 
have  settled  in  our  Northwestern  States,  where  most 
of  them  have  eventually  died,  but  no  cases  have  oc- 
curred among  those  associated  with  them.  On  the 
other  hand,  leprosy  has  extended  in  Louisiana,  in 
the  Sandwich  Islands,  and  in  many  other  parts  of 
the  world,  as  a  result,  apparently,  of  the  introduction 
of  cases  from  other  endemic  foci  of  infection. 

Morrow  believes  that  the  main  factors  which  lead 
to  the  propagation  of  the  disease  are  individual 
predisposition  and  insanitary  surroundings.  Certain 
authors  insist  that  a  fish  diet  has  the  effect  of  estab- 
lishing a  predisposition  to  the  disease.  In  support  of 


LEPROSY  185 

this  theory  they  call  attention  to  the  fact  that  the 
disease  is  more  prevalent,  in  certain  countries,  along 
the  sea-coast,  where  fish  contributes  a  considerable 
proportion  of  the  diet  of  the  inhabitants.  The 
influence  of  insanitary  surroundings  and  uncleanly 
habits  in  promoting  the  spread  of  the  disease  is  gen- 
erally admitted. 

The  conditions  among  the  peasantry  of  Norway, 
where  the  disease  is  quite  common,  are  stated  by 
Leloir  as  follows  : 

"  The  Norwegian  peasant  is  very  dirty.  The  greater  number 
of  the  peasants  have  never  taken  a  bath.  They  may  sometimes 
wash  (once  a  week)  the  hands  and  face,  and  the  feet  once  a 
year,  but  the  other  parts  of  the  body  are  not  washed  from  the 
day  of  their  birth  to  that  of  their  death.  Their  clothing  is  never 
taken  off  even  for  the  purposes  of  sleeping.  It  is  generally  made 
of  wool.  Their  garments  are  never  washed.  Dirt  is  allowed  to 
accumulate  upon  them,  and  when  not  too  rotten,  they  are  often 
transmitted  from  generation  to  generation.  They  live  promis- 
cuously gathered  together  in  a  small  house.  .  .  .  Dung  and 
filth  are  accumulated  around  the  house  amidst  pools  of  dirty 
water.  Often  pigs,  poultry,  and  other  domestic  animals  live  with 
the  family.  Almost  always  several  persons  sleep  in  the  same  bed, 
which  is  nothing  but  a  kind  of  wooden  chest  upon  which  are 
thrown  some  sheep  skins  or  goat  skins  which  are  scarcely  ever 
washed.  If  a  stranger  comes  he  shares  the  bed.  Everybody 
eats  at  the  same  table,  from  the  same  dish,  often  with  a  common 
spoon,  and  drinks  from  the  same  vessel." 

With  reference  to  the  habits  of  the  natives  of  the 
Sandwich  Islands  Mr.  Meyer,  Superintendent  of  the 
leper  settlement  at  Molokai,  says  : 


186  INFECTION  AND  IMMUNITY 

"  Their  modes  of  eating  are  so  extremely  careless  that  inocula- 
tion can  readily  take  place  through  the  mouth,  by  means  of 
the  saliva  or  otherwise.  They  pass  their  pipes  from  mouth  to 
mouth,  whether  any  of  their  number  is  a  leper  or  not;  they  kiss 
and  rub  their  noses  together;  they  eat  out  of  the  same  calabash 
with  their  fingers  and  drink  out  of  the  same  cup;  in  eating  fish 
or  meat  it  is  not  cut  up,  but  one  takes  the  meat  in  his  hand,  and, 
after  taking  a  bite,  passes  it  on.  They  drink  ava,  which  is  pre- 
pared by  others  chewing  the  root,  and  whether  the  one  chewing 
is  a  leper  or  not  is  not  considered.  Foreigners  also  become 
addicted  to  this  habit  of  ava  drinking,  and  it  is  remarkable 
that  most  of  the  foreigners  who  have  become  lepers  are  ava 
drinkers." 

These  habits  would  evidently  favour  the  communi- 
cation of  the  disease  in  the  manner  by  which  Morrow 
believes  this  usually  occurs,  which  is  shown  by  the 
following  quotation  from  his  valuable  article  in  the 
Twentieth  Century  Practice  of  Medicine.  He  says  : 
"In  the  vast  majority  of  cases,  I  believe  that  the 
vehicles  of  the  virus  through  which  contagion  is  ef- 
fected are  the  secretions  of  the  nose  and  mouth,  and 
that  the  port  of  entrance  is  the  mucous  membrane  of 
the  respiratory  and  intestinal  tract,  with  secondary  in- 
fection through  the  blood  or  lymphatic  system." 

There  is  little  doubt  that  leprosy  has  existed  from 
a  remote  antiquity,  although  there  is  some  difficulty 
in  identifying  the  disease  as  we  know  it  by  the  de- 
scriptions of  leprosy  given  by  Hebrew,  Greek,  and 
Arabian  authors.  In  the  Middle  Ages,  also,  although 
the  disease  was  far  more  prevalent  than  at  the  present 


LEPROSY  187 

day,  other  diseases  were,  no  doubt,  frequently  con- 
founded with  it.  The  disease  appears  to  have  existed 
in  Egypt,  in  India,  and  probably  in  other  parts  of 
Asia  long  before  it  was  introduced  to  the  countries 
of  Europe,  where  it  gained  its  widest  prevalence  be- 
tween the  sixth  and  twelfth  centuries  of  our  era.  Its 
decline  in  Europe  has,  to  a  great  extent,  been  pro- 
gressive since  the  fifteenth  century. 

In  Great  Britain,  the  disease  was  prevalent  during 
the  twelfth,  thirteenth,  and  fourteenth  centuries,  and 
numerous  "  leper  houses  "  existed.  The  disease  was 
less  common  during  the  following  centuries,  and  be- 
came practically  extinct  during  the  latter  part  of  the 
eighteenth  century,  its  final  seat  having  been  in  the 
Shetland  Islands.  In  1742  a  public  thanksgiving  was 
ordered  for  the  permanent  disappearance  of  leprosy 
from  the  Shetland  Islands.  The  last  leper  of  the 
Shetland  Islands,  it  is  stated,  died  in  the  Edinburgh 
Infirmary  in  1798  (Morrow).  In  southern  Europe 
the  disease  began  to  decline  towards  the  close  of  the 
seventeenth  century. 

At  the  present  day  India  and  China  are  the  chief 
centres  of  leprous  infection.  The  census  of  India  for 
1891  gives  the  total  number  of  lepers  in  that  country 
as  114,239.  The  disease  also  prevails  in  Cochin 
China,  in  the  Malay  Peninsula,  in  the  Dutch  East 
Indies,  in  the  Philippine  Islands,  and  in  Japan.  In 


i88  INFECTION  AND  IMMUNITY 

the  last-mentioned  country  it  was  reported,  in  1897, 
that  there  were  23,647  lepers,  a  majority  of  whom 
were  located  in  the  coast  region  of  the  islands.  In 
1893  the  total  number  of  lepers  in  Egypt  was  2204. 
In  Spain,  Portugal,  France,  and  Italy  a  limited  number 
of  cases  of  leprosy  may  be  found,  but  Great  Britain 
Holland,  Belgium,  Germany,  Austria,  Switzerland, 
and  Denmark  are  practically  free  from  the  disease— 
a  few  imported  cases  no  doubt  exist  in  each  of  these 
countries.  In  Norway,  which  for  many  years  has 
been  the  principal  infected  centre  in  Europe,  the 
number  of  cases  has  been  constantly  diminishing  dur- 
ing the  past  fifty  years.  In  1856  the  number  of  cases 
reported  was  2870,  in  1895  the  number  had  fallen  to 
688.  The  reduction  was  partly  due  to  the  emigra- 
tion of  lepers  to  other  countries  (287).  In  Russia 
1 200  cases  of  leprosy  were  reported  as  living  within 
the  limits  of  the  empire  in  the  year  1895,  when  an 
official  census  was  taken. 

In  South  America  and  in  the  West  Indies  there  are 
a  considerable  number  of  lepers,  especially  along  the 
coast  of  Brazil  and  of  British  Guiana.  The  disease 
also  exists  in  the  states  of  Central  America  and  in 
Mexico. 

Cases  of  leprosy  not  infrequently  arrive  in  the 
United  States  from  Norway,  from  China,  or  from 
the  Hawaiian  Islands,  but  the  policy  of  the  Govern- 


LEPROSY  189 

ment  and  State  health  authorities  now  is  to  return 
them  to  their  native  countries  when  practicable. 

We  have  in  the  United  States  one  centre  of  lep- 
rosy infection  which  has  existed  for  many  years,  and 
in  which  new  cases  are  still  developed  from  time  to 
time.  This  is  in  Louisiana.  According  to  Dr.  Dyer, 
who  has  made  a  special  investigation  with  reference 
to  leprosy  in  New  Orleans  and  vicinity,  270  cases 
have  developed  in  that  State  since  1878.  Of  these, 
171  were  born  in  Louisiana  and  39  were  born  in 
Europe. 

What  has  already  been  said  with  reference  to  the 
history  and  geographical  distribution  of  leprosy  indi- 
cates that  even  when  no  special  precautions  are  taken 
there  is  little  danger  that  the  disease  will  spread  to 
any  extent  in  countries  where  the  people  are  accus- 
tomed to  civilised  ways  of  living  and  pay  a  reason- 
able degree  of  attention  to  cleanliness.  Nevertheless, 
most  writers  upon  the  subject,  and  health  authorities, 
national  and  local,  insist  upon  the  isolation  of  lepers ; 
and,  where  there  are  a  considerable  number  of  these 
unfortunates,  upon  their  segregation  in  suitably  lo- 
cated colonies,  where  they  can  have  whatever  comfort 
and  enjoyment  is  possible  under  the  conditions  ex- 
isting in  such  isolated  localities,  while  at  the  same  time 
they  are  removed  from  the  possibility  of  communi- 
cating the  disease  to  others.  I  am  in  full  accord  with 


1 90  INFECTION  AND  IMMUNITY 

this  policy.  But  the  unreasonable  fear  of  lepers, 
which  has  existed  from  the  earliest  times,  and  is  often 
manifested  at  the  present  day,  is  evidently  not  justi- 
fied, in  view  of  the  very  remote  danger  of  the  disease 
being  contracted  by  any  ordinary  association  with 
them.  The  danger  from  tuberculosis  is  far  greater, 
and  this  disease  claims  nearly  150,000  victims  an- 
nually within  the  limits  of  the  United  States,  yet 
no  one  proposes  the  isolation  of  cases  of  pulmonary 
tuberculosis,  and  indeed  this  is  not  necessary  for  the 
prevention  of  the  disease  if  the  complete  disinfection 
of  all  infectious  material  can  be  secured — that  is,  of 
the  material  expectorated  by  those  suffering  from  the 
disease.  In  leprosy  it  will,  of  course,  be  advisable 
to  destroy  all  pus,  saliva,  etc.,  which  contains  the 
bacillus,  but  we  can  scarcely  insist  upon  the  rigid 
measures  of  disinfection  which  are  essential  for  the 
prevention  of  diphtheria,  or  smallpox,  in  view  of  the 
fact  that  painstaking  researches  fail  to  show  that 
the  disease,  under  ordinary  conditions  as  they  exist 
to-day,  is  communicated  to  healthy  individuals  who 
are  associated  in  an  intimate  way  with  the  sick. 


CHAPTER  IX 

DIPHTHERIA 

pvIPHTHERIA,  like  tuberculosis,  is  a  disease 
^^^  which  is  propagated  principally  through  the 
medium  of  the  sputa  of  infected  individuals,  which 
contains  in  large  numbers  the  specific  bacillus  to 
which  the  disease  is  due.  This  bacillus  effects  a 
lodgment  in  the  fauces,  or  in  the  posterior  nasal 
passages  of  susceptible  individuals  and  invades  the 
mucous  membrane,  causing  a  localised  inflammation 
and  a  fibrinous  exudation  —  so-called  "false  mem- 
brane." Its  first  appearance  is  very  commonly  upon 
the  tonsils.  As  the  disease  progresses  symptoms  of 
poisoning  by  the  deadly  toxin  of  the  diphtheria  bacil- 
lus are  developed. 

The  disease  is  more  frequent  and  more  fatal  in 
young  children  than  in  adults.  The  mortality  is 
greatest  in  infants  and  comparatively  low  in  children 
over  twelve  years  of  age.  The  disease  differs  greatly 
as  to  its  malignancy  during  different  epidemics. 


i92  INFECTION  AND  IMMUNITY 

There  are  evidently  many  different  breeds  of  the 
diphtheria  bacillus,  and  its  pathogenic  virulence  is 
increased  or  diminished  as  a  result  of  conditions  re- 
lating to  its  growth.  A  series  of  cases  in  very  sus- 
ceptible individuals  is  favourable  to  an  increase  in  the 
virulence  of  the  germ.  On  the  other  hand,  when 
obtained  from  the  throat  of  one  who  is  comparatively 
immune,  or  cultivated  in  artificial  media  outside  of 
the  body,  it  is  less  virulent. 

While  the  most  robust  children  are  subject  to 
attack,  delicate  and  poorly  nourished  children  are 
more  susceptible  and  more  likely  to  die.  A  chronic 
or  acute  catarrhal  inflammation  of  the  throat  or  nasal 
passages  predisposes  to  infection. 

The  bacillus  of  diphtheria  was  first  described  by 
the  German  pathologist,  Klebs,  in  1883,  and  the  fol- 
lowing year  the  fact  that  it  is  the  specific  cause  of 
this  disease  was  demonstrated  by  LofHer,  a  surgeon 
in  the  German  army  and  a  pioneer  in  bacteriological 
researches.  Hence  it  is  often  spoken  of  as  "  the 
Klebs-Loffler  bacillus."  Cultures  of  this  bacillus 
are  very  pathogenic  for  guinea-pigs,  rabbits,  chickens, 
pigeons,  and  cats,  and  to  a  less  extent  for  dogs, 
horses,  and  cattle.  Rats  and  mice  have  a  natural 
immunity.  The  immunity  of  certain  individuals  is 
shown  by  the  fact  that  when  associated  with  diph- 
theria patients  they  may  carry  virulent  diphtheria 


DIPHTHERIA  193 

bacilli  in  their  throats  without  manifesting  any  symp- 
toms of  the  disease.  Non-virulent  varieties  of  the 
diphtheria  bacillus  are  not  infrequently  found  in  the 
throats  of  healthy  persons.  Much  attention  has  been 
given  by  bacteriologists  to  the  question  as  to  how 
long  the  bacillus  may  persist  in  the  throats  of  con- 
valescents from  the  disease.  Drs.  Park  and  Beebe, 


FIG.  7.     Bacillus  of  diphtheria  ;  magnified  1000  diameters. 

of  the  New  York  Health  Department,  found  in  a 
series  of  605  cases  that  the  bacilli  disappeared  in  three 
days  in  304,  in  seven  days  in  176,  in  twelve  days  in  64, 
in  fifteen  days  in  36,  in  three  weeks  in  12,  in  four 
weeks  in  4,  and  in  nine  weeks  in  2.  This  shows  the 
necessity  for  expert  opinion  before  one  who  has  re- 
covered from  the  disease  is  allowed  to  associate  with 
susceptible  children. 


i94  INFECTION  AND  IMMUNITY 

It  is  now  recognised  by  physicians  that  "  mem- 
branous croup  "  is  due  to  the  diphtheria  bacillus,  and 
is  in  fact  a  form  of  diphtheria,  most  common  in  very 
young  children,  in  which  the  larynx  and  larger 
bronchial  tubes  are  the  seat  of  infection. 

The  total  number  of  deaths  reported  from  diph- 
theria in  the  last  census  year  (1900)  was  28,959. 
This  amounted  to  29  in  every  1000  deaths  from  all 
causes.  This  is  a  very  considerable  gain  upon  the 
proportion  shown  by  the  census  of  1890  (49.7  per 
1000).  The  death-rate  per  100,000  of  the  population 
was  45.2  ;  in  1890  it  was  more  than  twice  as  great 
(97.8).  This  gain  is  no  doubt  largely  due  to  the 
diminished  mortality  resulting  from  the  specific  treat- 
ment of  the  disease  with  diphtheria  antitoxin.  The 
death-rate  is  more  than  twice  as  great  in  cities  as 
in  rural  districts.  The  District  of  Columbia  has  the 
highest  rate  (75.4)  ;  and  the  State  of  Vermont  the 
lowest  (18.3).  It  is  evident  that,  in  view  of  our 
previous  statement  that  the  mortality  is  greater 
in  cities  than  in  rural  districts,  it  is  not  fair  to  com- 
pare the  District  of  Columbia  with  States  having  a 
large  rural  population.  As  compared,  however,  with 
the  average  rate  for  cities  (52.8)  the  record  of  the 
capital  city  of  the  nation  is  not  creditable.  It  is  due 
to  the  large  coloured  population  of  the  city  and 
the  comparatively  large  death-rate  among  negroes  as 


DIPHTHERIA  195 

compared  to  whites.  This  applies  only  to  children 
under  one  year  of  age  (345.7  per  100,000  coloured 
and  154.9  Per  100,000  white)  ;  beyond  this  age  the 
mortality  is  somewhat  greater  among  white  children. 

For  the  prevention  of  diphtheria  it  will  not  only  be 
necessary  to  disinfect  the  sputa  of  the  sick  and  all 
articles  liable  to  be  soiled  by  it,  but  also  to  isolate 
infected  individuals  until  all  danger  of  their  com- 
municating the  disease  has  passed.  The  measures 
recommended  in  the  previous  chapter  for  the  disin- 
fection of  tuberculous  sputum  apply  equally  well  for 
diphtheria.  The  diphtheria  bacillus  is  promptly  de- 
stroyed by  a  temperature  of  140°  Fahr.  (60°  C.) 
and  by  the  various  germicides  heretofore  mentioned. 
Boiling  water,  for  all  articles  which  can  be  sent  to 
the  laundry  and  for  the  disinfection  of  sputa  in  metal 
or  porcelain  receptacles,  is  the  cheapest  and  most  re- 
liable disinfectant,  but  it  will  usually  be  necessary  to 
use  a  solution  of  carbolic  acid  (three  to  five  per  cent.), 
or  one  of  the  other  coal-tar  products  (lysol,  creolin,  tri- 
cresol),  in  the  sick-room.  Woollen  clothing  and  other 
articles  which  would  be  injured  by  immersion  in  boil- 
ing water  may  be  disinfected  by  steam  or  by  formal- 
dehyd  gas. 

The  New  York  Health  Department  makes  the  fol- 
lowing judicious  recommendations  with  reference  to 
the  prevention  of  diphtheria : 


196  INFECTION  AND  IMMUNITY 

"If  possible,  one  attendant  should  take  entire  care  of  the  sick 
person,  and  no  one  else  besides  the  physician  should  be  allowed 
to  enter  the  sick-room.  The  attendant  should  have  no  com- 
munication with  the  rest  of  the  family.  The  members  of  the 
family  should  not  receive  or  make  visits  during  the  illness. 

"  The  discharges  from  the  nose  and  throat  must  be  received 
on  handkerchiefs  or  cloths,  which  should  be  at  once  immersed 
in  a  carbolic  solution  (made  by  dissolving  six  ounces  of  pure 
carbolic  acid  in  one  gallon  of  hot  water,  which  may  be  diluted 
with  an  equal  quantity  of  water).  All  handkerchiefs,  cloths, 
towels,  napkins,  bed  linen,  personal  clothing,  night-clothing,  etc., 
that  have  come  in  contact  in  any  way  with  the  sick  person,  after 
use  should  be  immediately  immersed,  without  removal  from  the 
room,  in  the  above  solution.  These  should  be  soaked  for  two  or 
three  hours,  and  then  boiled  in  water  or  soapsuds  for  one  hour. 

"  In  diphtheria  and  scarlet-fever,  great  care  should  be  taken  in 
making  applications  to  the  throat  or  nose,  that  the  discharges 
from  them  in  the  act  of  coughing  are  not  thrown  into  the  face  or 
on  the  clothing  of  the  person  making  the  applications,  as  in  this 
way  the  disease  is  likely  to  be  caught. 

"  The  hands  of  the  attendant  should  always  be  thoroughly  dis- 
infected by  washing  in  the  carbolic  solution,  and  then  in  soap- 
suds, after  making  applications  to  the  throat  or  nose,  and  before 
eating. 

"  Surfaces  of  any  kind  soiled  by  the  discharges  should  be  im- 
mediately flooded  with  the  carbolic  solution. 

"  Plates,  cups,  glasses,  knives,  forks,  spoons,  etc.  used  by  the 
sick  person  for  eating  and  drinking  must  be  kept  for  his  especial 
use,  and  under  no  circumstances  removed  from  the  room  or 
mixed  with  similar  utensils  used  by  others,  but  must  be  washed 
in  the  room  in  the  carbolic  solution  and  then  in  hot  soapsuds. 
After  use  the  soapsuds  should  be  thrown  into  the  water-closet 
and  the  vessel  which  contained  it  should  be  washed  in  the  carbolic 
solution. 

"  The  room  occupied  by  the  sick  person  should  be  thoroughly 
aired  several  times  daily,  and  swept  frequently  "  (we  think  it 
better  to  wipe  floors  with  cloths  wet  with  a  disinfecting  solution), 


DIPHTHERIA  197 

"  after  scattering  wet  newspapers,  sawdust,  or  tea-leaves  on  the 
floor  to  prevent  the  dust  from  rising.  After  sweeping,  the  dust 
upon  the  woodwork  and  furniture  should  be  removed  with  damp 
cloths.  The  sweepings  should  be  burned  and  the  cloths  soaked 
in  the  carbolic  solution.  In  cold  weather  the  sick  person  should 
be  protected  from  draughts  of  air  by  a  sheet  or  blankets  thrown 
over  his  bed  while  the  room  is  being  aired. 

4<  When  the  contagious  nature  of  the  disease  is  recognised 
within  a  short  time  after  the  beginning  of  the  illness,  after  the 
approval  of  the  Health  Department  Inspector,  it  is  advised  that 
all  articles  of  furniture  not  necessary  for  immediate  use  in  the 
care  of  the  sick  person,  especially  upholstered  furniture,  carpets, 
and  curtains,  should  be  removed  from  the  sick-room. 

"  When  the  patient  has  recovered  from  any  one  of  these  dis- 
eases the  entire  body  should  be  bathed  and  the  hair  washed  with 
hot  soapsuds,  and  the  patient  should  be  dressed  in  clean  clothes 
(which  have  not  been  in  the  room  during  the  sickness)  and  re- 
moved from  the  room.  Then  the  Health  Department  should  be 
immediately  notified,  and  disinfectors  will  be  sent  to  disinfect 
the  room,  bedding,  clothing,  etc.,  and  under  no  conditions  should 
it  be  again  entered  or  occupied  until  it  has  been  thoroughly  dis- 
infected. Nothing  used  in  the  room  during  the  sickness  should 
be  removed  until  this  has  been  done." 

Where  the  parents  have  not  ample  means  to  pro- 
vide for  the  services  of  a  trained  attendant,  and  a 
suitable  room  for  the  isolation  of  the  patient,  it  will 
be  much  better  for  the  sick  person,  and  for  all  con- 
cerned, to  send  the  patient  to  a  contagious-disease 
hospital,  when  this  is  practicable.  The  diphtheria 
bacillus  resists  desiccation  for  a  long  time  and  rooms 
or  clothing  soiled  with  material  containing  this  deadly 
disease  germ  remain  dangerous  for  months  if  they 
have  not  been  properly  disinfected. 


198  INFECTION  AND  IMMUNITY 

The  diphtheria  antitoxin  which  is  now  extensively 
and  successfully  used  in  the  specific  treatment  of  the 
disease  may  also  be  used  to  prevent  its  development 
in  persons  exposed  to  infection.  From  five  to  ten 
cubic  centimetres  of  a  reliable  antitoxin  is  used  for 
this  purpose.  This  is  injected  subcutaneously  and 
is  a  harmless  procedure  which  has  been  proved  to 
be  efficacious  in  most  cases,  or  at  least  to  greatly 
modify  the  severity  if  an  attack  occurs.  Where  child- 
ren have  been  exposed  to  infection,  or  under  cir- 
cumstances which  prevent  the  proper  isolation  of  a 
diphtheria  patient,  it  is  prudent  to  resort  to  such 
preventive  inoculations.  As  is  generally  known,  the 
antitoxin  is  usually  obtained  for  practical  purposes 
from  horses  which  have  been  rendered  immune  by 
repeated  and  gradually  increasing  doses  of  diphtheria 
toxin — that  is,  the  poisonous  substance  developed  by 
the  diphtheria  bacillus  during  its  growth  in  suitable 
culture  media.  The  antitoxin  is  contained  in  the 
blood  of  the  immune  animal,  and  the  clear  blood 
serum  which  separates  on  standing,  from  the  "clot," 
which  contains  the  red  and  white  blood  corpuscles,  is 
spoken  of  as  "  antitoxin "  and  is  used  in  the  treat- 
ment and  prevention  of  the  disease.  From  this  blood 
serum  a  more  concentrated  antitoxin  may  be  obtained 
by  chemical  methods,  but  this  has  not  come  into 
practical  use. 


CHAPTER  X 

INFLUENZA 

C  PI  DEM  1C  influenza  ("la  grippe")  is  an  infec- 
"  tious  disease  due  to  a  minute  bacillus  discovered 
by  the  German  bacteriologist  Pfeiffer  in  1892.  This 
bacillus  is  found  in  great  numbers  in  the  purulent 
bronchial  secretion  coughed  up  by  persons  suffering 
from  influenza  and  the  disease  is  propagated  by  con- 
tact with  the  sick  and  with  articles  infected  by  them, 
just  as  is  the  case  in  diphtheria,  or  whooping-cough. 
The  rapid  extension  and  wide  prevalence  of  the  dis- 
ease is  due  to  the  facts  that  persons  of  all  ages  are 
susceptible,  and  that  isolation  of  the  sick  and  disin- 
fection of  sputa  are  rarely  practised,  on  account  of  its 
comparatively  mild  character.  Nevertheless,  the  dis- 
ease is  attended  with  considerable  danger,  especially 
for  old  persons  or  those  in  feeble  health  ;  and  it  is  the 
direct  or  remote  cause  of  many  deaths.  The  offi- 
cial records  of  Prussia  for  1892  show  a  mortality  from 
this  disease  of  15,911,  of  whom  over  half  were  more 

IQ9 


200  INFECTION  AND  IMMUNITY 

than  sixty  years  of  age.  The  total  number  of  deaths 
in  the  United  States  during  the  census  year  1900 
was  16,645.  As  in  Germany  and  elsewhere  a  large 
proportion  of  the  deaths  occurred  in  persons  over 
sixty  years  of  age  or  among  young  children,  under 
five.  But  these  figures  by  no  means  represent  the 
total  mortality  from  the  disease.  Many  deaths  re- 


FIG.  8.     Bacillus  of  influenza  ;  magnified  1000  diameters. 

corded  as  due  to  pneumonia  are  the  result  of  a  pre- 
ceding attack  of  influenza.  Other  complications  or 
results  of  the  disease  which  may  have  a  fatal  termina- 
tion are  connected  with  the  brain  and  spinal  cord,  the 
heart  or  the  kidneys.  Serious  eye  and  ear  troubles, 
also,  not  infrequently  follow  an  attack  of  influenza. 

Wide-spread  epidemics  of  influenza  have  prevailed 
in  Europe  from  an  early  period.     It  prevailed  in  Italy, 


INFLUENZA  201 

Germany,  and  England  as  long  ago  as  1173,  and 
since  that  time  there  have  been  repeated  epidemics. 
The  epidemic  which  started  in  the  year  1510  was  the 
first  one  occurring  in  the  British  Islands  of  which  we 
have  authentic  and  accurate  accounts.  This  epidemic 
had  such  a  wide  distribution  that  it  is  said  to  have 
44  raged  all  over  Europe,  not  missing  a  family  and 
scarce  a  person  "  (Thomas  Short). 

Another  still  greater  epidemic,  or  "  pandemic," 
dates  from  the  year  1580.  We  cannot  spare  the 
space  for  an  historical  account  of  the  numerous  epi- 
demics which  occurred  during  the  seventeenth  and 
eighteenth  centuries,  but  will  pass  on  to  the  nine- 
teenth. 

In  1802  the  disease  made  its  appearance  in  France 
and  during  the  following  year  obtained  wide  exten- 
sion in  European  countries.  In  1807  it  was  gen- 
erally disseminated  in  North  America.  It  again 
prevailed  both  in  North  and  South  America  in  1815 
and  1816;  the  next  epidemic  in  the  United  States 
was  inaugurated  in  1824  and  lasted  for  several  years. 
The  epidemic  of  1833  was  apparently  confined  to  the 
Eastern  Hemisphere,  where  the  countries  of  Europe, 
Asia,  and  Northern  Africa  were  invaded.  It  is  said 
that  in  St.  Petersburg  "  not  one  person  escaped  the 
influenza"  during  this  epidemic.  The  next  extensive 
epidemic  in  Europe  was  during  the  years  1836-37; 


202  INFECTION  AND  IMMUNITY 

and  again  the  Eastern  Hemisphere  was  visited  in 
1847-48.  In  the  winter  of  1851  the  disease  obtained 
wide  prevalence  both  in  North  and  South  America. 
In  1857-58  it  again  prevailed  extensively  in  both 
hemispheres  and  in  some  localities  (Rome  and  Naples) 
was  attended  with  a  high  rate  of  mortality.  During 
the  winter  of  1874-75  it  again  prevailed  extensively 
in  Europe  and  America.  During  the  epidemic  of 
1889-90  the  disease  obtained,  within  a  brief  period,  a 
wider  extension  in  all  parts  of  the  world  than  in  any 
previous  epidemic.  This  pandemic  apparently  had 
its  origin  in  Central  Asia.  The  United  States  has 
not  been  free  from  the  disease  since  the  date  last 
mentioned,  and  some  very  susceptible  individuals,  es- 
pecially in  cities,  suffer  an  attack  almost  annually. 

The  incubation  period  is  comparatively  brief,  being 
from  two  to  six  days.  Those  whose  occupation  keeps 
them  out-of-doors  during  the  daytime  are  less  sub- 
ject to  attack  than  factory  hands  or  others,  who  are 
more  exposed  to  contagion  by  reason  of  their  liv- 
ing in  closed  rooms  containing  numerous  occupants. 
The  disease  prevails  to  some  extent  throughout  the 
year  but  the  largest  number  of  cases  occur  during  the 
winter  and  spring  months.  Catarrhal  conditions  of 
the  bronchial  and  nasal  mucous  membranes,  and  the 
meteorological  conditions  which  are  favourable  to 
"catching  cold"  constitute  predisposing  causes.  Per- 


INFLUENZA  203 

sons  who  live  in  over-heated  and  ill-ventilated  apart- 
ments are  also  especially  subject  to  attack.  The 
contagious  nature  of  the  disease  is  shown  by  the  fact 
that  an  initial  case  in  a  household,  a  school,  a  factory, 
or  a  prison  commonly  leads  to  a  local  epidemic  which 
may  include  all  of  those  exposed  to  infection. 

The  prevention  of  the  disease  under  existing  con- 
ditions seems  impracticable,  as  isolation  of  the  sick, 
and  especially  of  mild  cases  and  of  convalescents  who 
are  still  capable  of  communicating  the  disease,  is  a 
measure  which  is  not  likely  to  be  considered  with 
favour  by  the  public  and  has  not  been  seriously  pro- 
posed by  health  authorities.  Those  who  are  in  deli- 
cate health,  and  especially  elderly  persons,  should 
endeavour  to  avoid  contact  with  persons  suffering 
from  influenza.  And  those  suffering  from  the  disease 
should  make  it  a  matter  of  conscience  not  to  com- 
municate it  to  their  friends  by  untimely  visits,  by 
kissing,  etc.  For  one  who  recognises  the  contagious 
nature  of  the  malady  and  who  has  had  some  previ- 
ous personal  experience  as  to  the  discomfort  attend- 
ing an  attack,  it  is  not  pleasant  to  have  a  friend 
call  and  announce  the  fact  that  he,  or  she,  is  "  just 
recovering  from  an  attack  of  influenza,"  or  is  "  really 
too  sick  to  be  out,  but  could  not  resist  the  tempta- 
tion of  running  over  to  see  you  and  to  inquire  about 
the  children  "  —and  perhaps  bestows  a  kiss  upon  the 


204  INFECTION  AND  IMMUNITY 

"  little  dears."  Those  who  are  confined  to  the  house 
by  an  attack  should  by  all  means  spit  in  a  metal 
or  porcelain  receptacle  containing  a  disinfecting  solu- 
tion, and  other  members  of  the  household  should,  as 
far  as  is  practicable,  be  kept  from  their  room.  Those 
who  are  able  to  go  about  should  have  an  ample  pro- 
vision of  pocket-handkerchiefs  and  these  should  be 
immersed  in  a  disinfecting  solution  upon  their  return 
to  the  house. 

Fortunately  the  influenza  bacillus  is  soon  killed  by 
desiccation  and  by  exposure  to  sunlight.  An  effectual 
way  of  disinfecting  woollen  clothing,  stuffed  furniture, 
etc.,  will  therefore  be  to  expose  it  in  the  open  air. 
The  bacilli  in  dried  sputum  do  not  survive  more  than 
twenty-four  hours  and  a  majority  of  them  are  killed  in 
seven  or  eight  hours.  Diffuse  daylight  also  hastens 
their  death.  It  is  therefore  unnecessary  to  resort  to 
the  rigid  measures  of  disinfection  recommended  in 
diphtheria  and  tuberculosis,  in  which  diseases  the 
specific  germs  resist  desiccation  for  a  long  time. 
Free  ventilation  for  two  or  three  days  and  exposure 
of  infected  articles  in  the  open  air  will  ensure  the  dis- 
infection of  the  room  and  its  contents.  The  disease 
is  no  doubt  largely  spread  by  the  minute  droplets 
ejected  by  the  sick  in  coughing  or  sneezing,  each  one 
of  which  contains  thousands  of  influenza  bacilli. 


CHAPTER   XI 
PNEUMONIA 

T  OBAR  or  "  croupous "  pneumonia  is  due  to  a 
*"^  micrococcus  discovered  by  the  present  writer  in 
1880  and  since  demonstrated  to  be  the  cause  of  this 
infectious  disease.  The  micrococcus  of  pneumonia  is 
found  in  great  numbers  in  the  exudate  which  fills  the 
air  cells  of  the  portion  of  the  lung  involved  (one  or 
more  lobes)  and  in  the  sticky  sputum  coughed  up 
by  the  patient.  This  is  "  rusty  "  in  appearance  on  ac- 
count of  the  presence  of  red  blood-corpuscles.  In 
fatal  cases  of  pneumonia  the  micrococcus  is  not  infre- 
quently found,  also,  in  the  blood  of  the  infected  indi- 
vidual, but  as  a  rule  the  disease  may  be  regarded  as  a 
localised  infection.  The  symptoms  are  due  in  part  to  a 
deficient  supply  of  oxygen  from  the  occlusion  of  the 
air  cells  in  one  or  more  lobes  and  in  part  to  the 
absorption  of  the  toxin  produced  by  the  micrococcus. 
The  fatality  of  the  disease  depends  largely  upon  the 

extent  of  lung  tissue  involved  and  also  upon  the  age 

205 


206  INFECTION  AND  IMMUNITY 

and  vital  resisting  power  of  the  individual  attacked. 
Depressing  influences  of  all  kinds  predispose  to  an 
attack,  and  especially  alcoholism,  malnutrition,  and 
insanitary  surroundings.  Pneumonia  also  frequently 
occurs  as  a  complication  of  other  infectious  diseases- 
measles,  influenza,  typhoid  fever. 

It  is  most  prevalent  during  the  spring  months.    In 


FIG.  9.  Micrococcus  of  pneumonia;  magnified  1000  diameters.  A,  with 
"  capsule,"  as  seen  in  the  blood  of  an  infected  animal ;  B,  as  seen  in  a  culture 
fluid. 

the  United  States  the  area  of  greatest  prevalence  is  the 
Middle  Atlantic  Coast  region.  The  Gulf  Coast  region 
and  the  South  Atlantic  Coast  region  have  the  smallest 
proportion  of  deaths  from  this  disease.  The  North  At- 
lantic Coast  region,  the  Interior  Plateau,  the  Central 
Appalachian  region  and  the  region  of  the  Great  North- 
ern Lakes  have  all  about  the  same  rate  (103  to  106 


PNEUMONIA  207 

per  1000  deaths  from  all  causes).  The  greatest  mor- 
tality occurs  in  children  under  five  years  of  age  (388.6 
out  of  1000  deaths  from  this  disease). 

The  total  number  of  deaths  reported  as  due  to 
pneumonia  during  the  census  year  1900  was  105,971, 
the  proportion  in  1000  deaths  from  all  causes  being 
1 06.  i.  This  is  an  increase  over  the  ratio  shown 
by  the  preceding  census  (90.6). 

The  State  of  New  York  gave  the  highest  rate 
(228.4)  and  Michigan  the  lowest  (109.3).  The  rate 
was  considerably  higher  in  cities  than  in  the  rural 
districts,  and  the  census  of  1900  shows  an  increase  in 
the  cities  and  a  diminished  rate  in  the  country  over 
the  rates  of  1890.  The  death-rate  among  the  col- 
oured population  (349  per  1000  deaths)  was  consider- 
ably greater  than  among  whites  (184.8).  It  was 
also  larger  for  foreign-born  whites  than  for  native 
whites.  The  death-rate  from  pneumonia  per  100,000 
of  the  population  was  190  in  1900  and  186.9  in  1890. 
These  figures  show  that  pneumonia  ranks  with  tuber- 
culosis as  a  cause  of  mortality  in  the  United  States 
and  that  while  the  number  of  deaths  from  the  last- 
mentioned  disease  is  diminishing  there  has  been 
a  decided  increase  in  the  number  of  deaths  from 
pneumonia  during  the  past  ten  years. 

The  recent  statistics  of  the  city  of  Chicago  show 
a  notable  increase  in  the  number  of  deaths  from  this 


208  INFECTION  AND  IMMUNITY 

disease.  In  the  Bulletin  of  the  Health  Department 
of  that  city  for  the  month  of  May,  1903,  the  follow- 
ing statement  is  made  : 

"Since  the  first  of  January  there  have  been  2891  deaths  from 
pneumonia,  as  compared  with  1321  from  consumption  and  1238 
from  all  other  communicable,  contagious,  or  infectious  diseases, 
including  diphtheria,  erysipelas,  influenza,  measles,  puerperal 
fever,  scarlet  fever,  smallpox,  typhoid  fever,  and  whooping-cough. 
This  is  an  excess  of  382  pneumonia  deaths  over  the  deaths  from 
all  the  other  preventable  diseases — 1570,  or  118.8  per  cent,  more 
than  the  deaths  from  consumption,  and  1653,  or  133.5  Per  cent- 
more  than  those  from  the  other  specified  diseases." 

The  micrococcus  of  pneumonia,  unlike  the  tubercle 
bacillus,  is  able  to  live  in  the  mouths  of  healthy  per- 
sons, where  it  finds  the  necessary  pabulum  for  its  mul- 
tiplication in  the  normal  salivary  secretions.  While 
pneumonia  may  prevail  as  an  epidemic,  as  a  result  of 
the  transmission  of  the  disease  from  the  sick  to  those 
associated  with  them,  it  is  well  known  that  many  soli- 
tary cases  occur,  in  families,  which  cannot  be  traced 
to  preceding  cases  and  in  which  the  disease  does  not 
spread,  although  no  precautions  have  been  taken  in 
the  way  of  isolating  the  patient  or  disinfecting  his 
sputa.  The  infection  in  such  cases  probably  results 
from  the  presence  of  the  micrococcus  in  the  salivary 
secretions  of  an  individual  whose  lungs,  as  a  result  of 
"  catching  cold "  or  of  an  attack  of  measles  or  of 
influenza,  have  become  vulnerable,  — that  is,  are  sus- 


PNEUMONIA  209 

ceptible  to  infection  because  of  a  localised  congestion 
or  inflammation  of  the  mucous  membrane,  or  a  low- 
ered vitality  of  the  tissues  due  to  some  of  the  causes 
previously  mentioned  (alcoholism,  crowd-poisoning, 
etc).  My  own  researches  and  those  of  other  investi- 
gators show  that  this  micrococcus  is  present  in  the 
salivary  secretions  of  a  considerable  proportion  of 
healthy  persons,  both  in  this  country  and  in  Europe. 
Also,  that  it  varies  greatly  in  pathogenic  virulence  as 
obtained  from  this  source  and  from  the  sputa  of  pa- 
tients with  pneumonia. 

Epidemics  of  pneumonia,  in  prisons,  and  on  ship- 
board, have  occurred  with  sufficient  frequency  to  show 
that  the  disease  may  be  communicated  by  the  sick  to 
those  associated  with  them.  That  this  does  not  occur 
more  frequently  is  probably  due  to  the  fact  that  pa- 
tients with  pneumonia  are  confined  to  bed  and  that 
the  abundant  expectoration,  among  decent  people, 
could  scarcely  fail  to  be  deposited  in  a  receptacle  of 
some  kind,  or  to  be  wiped  from  the  mouths  by  hand- 
kerchiefs or  cloths  which  are  destroyed  by  fire  or  sent 
to  the  laundry.  Also  to  the  fact  that  the  micrococcus 
of  pneumonia  has  far  less  resisting  power  to  desicca- 
tion than  the  tubercle  bacillus  or  the  diphtheria  bacil- 
lus and  would  be  less  likely  to  survive  in  dust.  The 
tenacious  sticky  nature  of  the  sputa  also  prevents,  to 
a  great  extent,  the  coughing  up  of  minute  droplets, 


2 1 o  INFECTION  AND  IMM UNITY 

which  in  tuberculosis  and  in  influenza  play  an  im- 
portant part  in  the  propagation  of  the  disease.  The 
micrococcus  of  pneumonia  may,  however,  retain  its 
vitality  for  a  considerable  time  in  dried  masses  of 
sputum.  It  is  destroyed  by  exposure  for  a  few  hours 
to  direct  sunlight,  and  by  a  temperature  of  140°  Fahr. 
within  a  few  minutes ;  also  by  all  germicidal  agents 
in  comparatively  small  proportion.  The  directions 
already  given  for  the  disinfection  of  the  sputa  of  pa- 
tients suffering  from  tuberculosis  or  diphtheria  apply 
as  well  to  the  material  expectorated  by  patients  with 
pneumonia,  and  this  should  never  be  neglected. 

The  prevention  of  pneumonia  will,  to  a  large  ex- 
tent, depend  upon  the  avoidance  by  individuals  of 
the  predisposing  and  exciting  causes  of  the  disease. 
Proper  food,  proper  exercise,  dress  suitable  to  the 
climate  and  season,  avoidance  of  all  excesses,  and  es- 
pecially of  the  habitual  use  of  alcoholic  drinks,  will 
all  tend  to  preserve  the  individual  from  infection  by 
the  micrococcus  of  pneumonia.  On  the  other  hand 
insufficient  food,  insufficient  clothing,  alcoholic  ex- 
cesses, insanitary  surroundings,  and  a  recent  attack  of 
certain  other  infectious  diseases  (measles,  influenza, 
typhoid  fever)  are  potent  predisposing  causes.  Ex- 
posure to  cold,  to  draughts,  or  wet  feet  may,  in  con- 
junction with  the  presence  of  the  specific  micrococcus, 
become  the  direct  exciting  cause  of  an  attack. 


CHAPTER  XII 
WHOOPING-COUGH 

HOOPING-COUGH  is  another  infectious  dis- 
ease in  which  the  germ  is  no  doubt  present  in 
the  secretions  from  the  mucous  membrane  of  the  re- 
spiratory passages,  although  this  germ  has  not  yet 
been  demonstrated  to  the  entire  satisfaction  of  the 
medical  profession.  The  disease  is  propagated  by 
contact  or  close  association  with  the  sick,  but  the  in- 
fection does  not  persist  in  the  sick-room  or  attached 
to  the  clothing  of  the  sick,  as  is  the  case  in  diph- 
theria, measles,  and  scarlet  fever.  Probably  the  germ 
quickly  perishes  outside  of  the  bodies  of  the  suscept- 
ible individuals  who  serve  to  propagate  it.  It  has 
been  noted  that  the  disease  is  rarely  conveyed  by 
a  third  person  and,  when  the  clothing  of  those  in  at- 
tendance on  the  sick  is  changed,  the  danger  of  its 
being  transmitted  in  this  way  is  very  slight.  But  sus- 
ceptible children  contract  the  disease  after  very  brief 
contact  with  one  suffering  from  it.  The  infection 

211 


212  INFECTION  AND  IMMUNITY 

can  be  conveyed  from  the  very  outset  of  the  attack, 
and  probably  in  protracted  cases  for  several  months — 
just  how  long  has  not  been  definitely  determined. 
The  susceptibility  to  the  disease  among  children  is 
very  great,  but  diminishes  with  advancing  age.  Adults 
and  even  old  persons,  however,  occasionally  suffer  an 
attack.  The  immunity  resulting  from  a  single  attack 
is  very  great. 

The  number  of  deaths  reported  from  whooping- 
cough,  in  the  United  States,  during  the  census  year 
1900  was  9958.  The  death-rate  per  100,000  of  the 
population  was  12.7.  The  comparatively  non-fatal 
character  of  the  disease  is  shown  by  these  figures,  as 
it  is  one  of  the  commonest  and  most  widely  spread  of 
infectious  diseases.  A  considerable  number  of  deaths 
are,  however,  indirectly  due  to  an  attack  of  this  dis- 
ease as  it  is  recognised  as  one  of  the  predisposing 
causes  of  tuberculosis.  The  death-rate  in  the  United 
States  is  more  than  twice  as  great  among  coloured 
children  as  among  whites.  There  has  been  a  con- 
siderable decrease  in  the  mortality  from  whooping- 
cough  during  the  ten  years  ending  in  1900.  The 
census  returns  show  that  the  greatest  mortality  occurs 
among  infants,  less  than  one  year  of  age.  Beyond 
the  age  of  five  the  mortality  is  very  slight.  The 
months  of  greatest  mortality  are  March,  April,  and 
August  ;  of  lowest,  October  and  November. 


WHOOPING-COUGH  213 

In  the  prevention  of  this  disease  isolation  of  the 
sick  must  be  given  the  first  place.  Children  and 
especially  young  children  should  be  carefully  guarded 
from  exposure  to  infection.  The  mucus  coughed  up 
by  the  sick  should  be  received  upon  handkerchiefs  or 
squares  of  muslin  and  these  should  be  placed  in  a 
disinfecting  solution  or  burned.  Free  ventilation  of 
the  apartments  occupied  by  the  sick  and  prolonged 
exposure  of  infected  articles  to  the  sun  and  air  will 
suffice  for  the  disinfection  of  the  sick-room  and  its 
contents.  Isolation  of  the  patient  should  be  con- 
tinued so  long  as  the  characteristic  paroxysms  of 
coughing  continue  and  for  a  few  days  after  they 
cease.  The  recurrence  of  a  spasmodic  cough  after 
this  time,  if  two  or  three  months  has  elapsed  since 
the  outset  of  the  attack,  does  not  call  for  renewed 
isolation  of  the  patient,  as  such  spasmodic  cough- 
ing is  not  unusual  after  all  danger  of  infection  has 
passed. 


CHAPTER  XIII 

SMALLPOX 

TJAVING  given  some  account  of  the  causes  and 
prevention  of  the  "  filth  diseases "  and  of  the 
diseases  which  are  communicated  through  the  medium 
of  material  coughed  up  from  the  lungs  or  upper  air- 
passages  of  infected  individuals,  I  shall  now  briefly 
consider  that  group  of  infectious  diseases  known 
under  the  general  name  of  "eruptive  fevers,"  and  first 
in  importance  comes  smallpox.  This  disease,  which 
was  formerly  a  scourge  of  the  human  race,  has  been 
largely  robbed  of  its  terrors  by  vaccination. 

There  is  reason  to  believe  that  smallpox  has  pre- 
vailed in  India  and  China  from  a  remote  antiquity. 
It  was  probably  introduced  into  the  British  Islands 
about  the  year  1241.  From  the  end  of  the  thirteenth 
century  until  the  general  adoption  of  vaccination  as 
a  preventive  measure  smallpox  ranked  as  the  most 
destructive  of  the  pestilential  diseases.  Lord  Ma- 
caulay  describes  the  ravages  of  this  disease  in  pre- 

vaccination  times  as  follows  : 

214 


SMALLPOX  215 

"  That  disease,  over  which  science  has  since  achieved  a  series 
of  glorious  and  beneficent  victories,  was  then  the  most  terrible 
of  all  the  ministers  of  death.  The  havoc  of  the  plague  had  been 
far  more  rapid;  but  the  plague  had  visited  our  shores  only  once 
or  twice  within  living  memory;  and  the  smallpox  was  always 
present,  filling  the  churchyards  with  corpses,  tormenting  with 
constant  fears  all  whom  it  had  not  stricken,  leaving  on  those 
whose  lives  it  spared  the  hideous  traces  of  its  power, — turning  the 
babe  into  a  changeling  at  whom  the  mother  shuddered  and 
making  the  eyes  and  cheeks  of  the  betrothed  maiden  objects  of 
horror  to  the  lover." 

In  England  and  Wales  the  annual  mortality  from 
smallpox  prior  to  the  year  1796  was  about  3000 
for  every  million  of  the  inhabitants.  Less  than  a 
century  later,  in  1890,  the  total  number  of  deaths 
from  this  disease  during  an  entire  year  was  only 
fifteen.  In  Germany,  where  vaccination  is  compul- 
sory and  children  must  be  revaccinated  at  the  age 
of  twelve,  smallpox  is  almost  unknown. 

In  the  year  1888  there  were  but  no  deaths  from 
this  disease  in  the  entire  German  Empire.  In  France, 
where  vaccination  is  very  much  neglected,  the  mor- 
tality from  smallpox  is  about  35  per  100,000  inhabit- 
ants (1889).  Brouardel,  a  French  author,  from  a 
consideration  of  the  statistics  of  the  two  countries, 
arrives  at  the  conclusion  that  "  revaccination  ought 
to  be  made  obligatory."  In  Scotland,  when  vaccina- 
tion was  optional  (1855-64),  the  mortality  was  con- 
siderable (340  per  million  inhabitants),  but  when  it 


216  INFECTION  AND  IMMUNITY 

was  made  compulsory  the  number  of  deaths  fell  to 
80  per  million.  In  Sweden  the  mortality  in  the  eight- 
eenth century  exceeded  2000  per  million  of  the  in- 
habitants. From  1801  to  1815,  when  vaccination  was 
largely  practised  but  was  not  compulsory,  the  death- 
rate  fell  to  631  per  million.  Since  this  preventive 
measure  has  been  made  compulsory  the  rate  has  con- 
tinued to  fall  until  it  is  not  more  than  8  per  million. 

The  immunity  resulting  from  vaccination  is  not 
absolute  and  it  is  well  known  that  very  susceptible 
persons  may  suffer  a  second  or  even  a  third  attack  of 
smallpox.  But  attacks  in  vaccinated  persons  are  com- 
paratively rare  and  comparatively  mild. 

This  is  shown  by  statistics  collected  by  the  London 
Board  of  Health,  which  show  that  the  mortality 
among  unvaccinated  persons  was  20.85  ^>  while  among 
the  vaccinated  it  was  only  3.40$.  The  gradual  loss 
of  immunity  after  vaccination  is  established  by  the 
well-known  fact  that  revaccination  after  a  longer  or 
shorter  interval  is  successful  in  a  considerable  pro- 
portion of  the  cases.  This  is  therefore  to  be  recom- 
mended whenever  smallpox  is  prevalent. 

As  a  result  of  neglect  of  vaccination  an  epidemic 
occurred  in  Sheffield,  England,  some  years  ago. 
Statistics  collected  during  this  epidemic  (1887-88) 
show  that  among  children  less  than  ten  years  of  age 
the  vaccinated  were  attacked  in  the  proportion  of 


SMALLPOX  217 

5  per  thousand,  and  the  unvaccinated  in  the  pro- 
portion of  101  per  thousand.  The  death-rate  among 
the  vaccinated  was  about  one-tenth  of  one  per  cent, 
and  among  the  unvaccinated  44  per  cent.  Similar 
and  even  more  favourable  statistics  could  be  pre- 
sented from  other  parts  of  England  and  from  all 
countries  where  vaccination  is  systematically  practised. 

The  total  number  of  deaths  reported  from  small- 
pox, in  the  United  States,  during  the  last  census 
year  was  3484.  If  the  mortality  had  corresponded 
with  that  of  England  and  Wales  before  the  introduc- 
tion of  vaccination  it  would  have  amounted  to  more 
than  210,000. 

The  practical  stamping  out  of  smallpox  in  the  Dis- 
trict of  Holguin,  Cuba,  and  in  the  island  of  Porto 
Rico,  since  the  Spanish-American  War,  by  the  vac- 
cination of  all  the  inhabitants,  under  the  direction  of 
the  military  authorities  of  the  United  States,  is  a 
matter  of  record  in  my  annual  reports  as  Surgeon- 
General  of  the  Army  for  the  years  1899  an<^  1900. 
In  my  report  for  1899  I  say : 

"  It  is  understood  that  the  occurrence  of  smallpox  among  our 
troops  in  the  Philippines  gave  rise  in  England,  where  the  pro- 
tective influence  of  vaccination  was  under  discussion  at  the  time, 
to  the  claim  that,  as  vaccination  was  compulsory  in  the  United 
States  Army,  and  carried  out  under  military  rules,  the  presence 
of  the  disease  among  our  soldiers  showed  the  inefficiency  of  the 
process.  This  claim  of  the  opponents  of  vaccination  is  not  well 


2i8  INFECTION  AND  IMMUNITY 

taken.  On  the  contrary,  the  history  of  vaccination  and  of  small- 
pox in  the  United  States  Army  suffices  in  itself  to  demonstrate 
that  protection  from  the  disease  is  proportioned  to  the  care  with 
which  vaccination  is  performed.  .  .  .  Although  this  disease 
has  prevailed  in  many  parts  of  the  United  States  during  the  past 
fifteen  years  (1883  to  1897),  and  frequently  with  epidemic  vio- 
lence, among  the  civil  population  in  the  immediate  vicinity  of 
military  posts,  there  occurred  only  20  scattered  cases,  of  which  4 
were  fatal,  in  a  mean  strength  of  25,000  men." 

The  cases  which  occur  in  various  parts  of  the  coun- 
try, from  time  to  time,  are  for  the  most  part  among 
unvaccinated  individuals.  For  example,  in  the  city 
of  Chicago,  the  Bulletin  of  the  Health  Department 
for  the  month  ending  May  31,  1903,  says  : 

"  During  the  month  forty- five  cases  of  smallpox 
were  discovered  and  removed  to  the  Isolation  'Hos- 
pital. Of  these  thirty-nine  never  had  been  vaccinated  ; 
six  had  old,  imperfect  marks,  said  to  be  from  vaccina- 
tion in  childhood.  Fifteen  were  unvaccinated  child- 
ren under  six  years  of  age." 

It  is  unnecessary  to  give  any  further  facts  in  support 
of  the  protective  value  of  vaccination,  which,  since 
the  discovery  of  Jenner  in  1796,  has  been  established 
by  unimpeachable  statistical  data  in  all  parts  of  the 
civilised  world.  But  there  are  certain  persons  whose 
minds  are  not  penetrated  by  the  logic  of  facts,  or  who 
have  not  taken  the  pains  to  make  themselves  familiar 
with  these  facts,  who  still  oppose  vaccination  on  the 
ground  that  it  has  no  value  as  a  preventive  measure. 


SMALLPOX  219 

Recent  researches  seem  to  prove  that  the  small- 
pox germ  multiplies  in  the  epithelial  cells  of  that 
portion  of  the  skin  which  is  involved  in  the  pustules 
which  are  characteristic  of  the  disease.  This  germ  is 
extremely  minute  and  it  has  not  been  cultivated  in 
artificial  media.  It  does  not  belong  to  the  same  class 
as  the  germs  of  typhoid  fever,  cholera,  diphtheria, 
etc.  (the  bacteria),  but  to  the  protozoa. 

It  is  generally  recognised  that  smallpox  patients 
must  be  isolated  and  cared  for  by  immune  attendants, 
and  that  clothing  and  all  articles  exposed  to  infection 
must  be  thoroughly  disinfected.  This  is  especially 
important,  as  the  infectious  agent  or  germ  is  given  off 
from  the  general  surface  of  the  body,  attached  to 
epithelium,  pus  cells,  etc.  This  infectious  agent  may 
retain  its  capacity  for  harm  (vitality)  for  months  in 
spite  of  desiccation.  An  instance  is  given  by  Dr. 
Buck,  of  New  York,  in  which  an  unvaccinated  infant, 
when  two  months  -  old,  contracted  smallpox  in  the 
room  in  which  it  was  born  and  in  which  a  case  of 
smallpox  had  occurred  two  years  previously. 

The  danger  of  infection  from  a  patient  before  the 
eruption  has  developed  is  very  slight  if  any  and  it  is 
chiefly  through  pus  and  scabs  which  are  formed  at  a 
later  stage  of  the  disease  that  the  malady  is  propa- 
gated. The  time  which  elapses  after  exposure  before 
the  first  symptoms  of  the  disease  are  manifested  is 


220  INFECTION  AND  IMMUNITY 

usually  twelve  days  and  the  duration  of  the  disease  in 
cases  ending  in  recovery  is  about  three  weeks.  That 
the  smallpox  virus  may  be  carried  a  considerable  dis- 
tance through  the  air  by  currents  of  wind,  and  the 
disease  thus  be  propagated,  seems  to  be  well  estab- 
lished by  the  observations  of  certain  English  authori- 
ties upon  the  subject.  But  it  is  not  certain  whether 
it  is  directly,  as  dust  carried  by  the  wind,  or  indirectly, 
attached  to  the  feet  of  flies  which  have  been  in  con- 
tact with  the  pustules  on  the  body  of  a  smallpox  pa- 
tient, that  the  disease  has  been  conveyed  in  the 
instances  which  have  been  recorded.  The  extreme 
limit  to  which  the  disease  is  likely  to  be  commun- 
icated in  this  way  probably  does  not  exceed  a  mile. 
The  disinfection  of  the  room  occupied  by  a  small- 
pox patient,  and  all  its  contents,  calls  for  the  most 
careful,  intelligent,  and  thorough  measures.  Only 
absolutely  necessary  articles  should  be  left  in  the  room 
and  it  is  well  to  have  screens  in  the  windows  to  exclude 
flies.  Abundant  ventilation  is  important.  While  oc- 
cupied by  the  patient,  floors,  window-ledges,  and  all 
places  where  dust  is  liable  to  accumulate  should  be 
frequently  wiped  with  a  cloth  wet  with  a  suitable  dis- 
infecting solution  (5  %  solution  of  carbolic  acid  or 
i  :  1000  solution  of  corrosive  sublimate).  All  washable 
articles  which  have  been  in  contact  with  the  sick  per- 
son or  in  use  in  the  sick-room  should  be  immersed  in 


SMALLPOX  221 

a  disinfecting  solution  in  the  room  or  in  an  adjoining 
room.  Subsequently  they  are  to  be  subjected  to  the 
action  of  steam  or  of  boiling  water.  Woollen  clothing, 
carpets,  curtains,  etc.,  are  best  disinfected  by  steam. 
But  the  room  and  its  contents,  after  the  patient  has 
left  it,  may  be  disinfected  with  formaldehyd  gas  or  by 
fumigation  with  burning  sulphur.  This  disinfection 
should,  however,  be  attended  to  by  an  expert  and  is 
to  be  followed  by  thorough  washing  of  all  surfaces 
with  a  disinfecting  solution,  and  subsequent  scrubbing 
with  hot  soap-suds,  whitewashing  of  plastered  walls, 
free  ventilation,  and  exposure  of  clothing,  bedding, 
etc.,  in  the  open  air  to  direct  sunlight. 

With  reference  to  vaccination,  which  is  our  chief 
reliance  for  preventing  the  spread  of  the  disease,  we 
recommend  the  vaccination  of  infants  and  revaccina- 
tion  at  the  age  of  ten  or  twelve,  as  practised  in  Ger- 
many. After  this  tests  of  the  immunity  of  persons 
of  any  age  should  be  made,  by  revaccination,  when- 
ever smallpox  is  prevalent,  or  when  the  individual  is 
about  to  travel  in  countries  where  this  preventive 
measure  is  neglected  or  carried  out  in  an  indifferent 
manner. 

Chicken-pox  is  a  highly  contagious  disease  which 
fortunately  is  mild  in  character  and  does  not  contribute 
to  our  mortality  statistics.  The  fact  that  mild  cases 
of  smallpox  have  not  infrequently  been  mistaken  for 


222  INFECTION  AND  IMMUNITY 

varicella,  or  chicken-pox,  should  be  borne  in  mind. 
This  mistake  has  been  responsible  for  the  spread  of 
smallpox  in  numerous  instances  and  is  to  be  guarded 
against  by  the  isolation  of  the  sick  and  the  measures 
of  disinfection  heretofore  recommended  for  prevent- 
ing the  extension  of  that  disease.  The  period  of 
incubation  in  chicken-pox  is  fourteen  days.  The 
germ  of  this  disease  has  not  been  discovered,  but  it 
has  been  demonstrated  that  it  is  present  in  the 
"  lymph  "  contained  in  the  vesicles  which  are  charac- 
teristic of  the  disease. 


CHAPTER   XIV 

SCARLET  FEVER 

OCARLET  fever  is  widely  prevalent  in  the  coun- 
^  tries  of  Europe  and  in  North  and  South  America, 
but  is  scarcely  known  in  Asia  and  in  Africa.  It  is 
said  to  occur  occasionally  in  China,  but  to  be  un- 
known in  Japan.  It  is  impossible  to  say  how  long 
it  has  prevailed  in  Europe,  but  the  first  to  clearly 
recognise  it  as  a  distinct  specific  disease  was  the 
famous  English  physician  Sydenham  (1685).  It  was 
not  introduced  to  North  America  until  about  the 
year  1735  and  first  appeared  in  South  America  about 
1830. 

The  germ  of  scarlet  fever  has  not  been  demon- 
strated but,  as  is  well-known,  the  scarlet  fever  patient 
gives  off  from  the  surface  of  his  body  infectious 
material  by  means  of  which  the  disease  may  be  com- 
municated, either  directly  or  indirectly,  to  other  sus- 
ceptible individuals.  This  consists  essentially  of 
cast-off  ("  desquamated ")  epithelium,  to  which  the 

223 


224  INFECTION  AND  IMMUNITY 

infectious  agent,  or  germ,  is  attached,  and  which 
may  retain  its  infecting  power  for  many  months. 
The  sputa  of  scarlet  fever  patients  also  contains  the 
germ  and  by  some  physicians  is  believed  to  be  to  a 
large  extent  responsible  for  the  spread  of  the  dis- 
ease. As  the  mucous  membrane  of  the  mouth  and 
throat  is  involved  in  the  eruption  which  is  character- 
istic of  the  disease  and  is  in  fact  the  locality  where 
this  eruption,  followed  by  desquamation  of  the  epi- 
thelium, may  first  be  observed,  it  is  evident  that  all 
expectorated  material  must  contain  the  infectious 
agent.  The  disease  may  be  communicated  by  the 
scarlet  fever  patient  at  any  time  during  the  period  of 
desquamation,  which  may  last  for  a  month,  or  more. 
The  period  during  which  the  patient  should  be  isol- 
ated, dating  from  the  outset  of  the  attack,  is  gen- 
erally fixed  at  six  weeks.  The  infection  may  persist 
in  clothing  and  bedding,  in  use  during  the  period  of 
desquamation,  or  exposed  in  the  sick-room,  for  a 
year  or  more. 

Certain  persons  seem  to  have  a  natural  immunity 
to  scarlet  fever  and  escape  the  disease  although  re- 
peatedly exposed  to  it.  In  some  instances,  no  doubt, 
this  failure  to  contract  the  disease  is  due  to  a  pre- 
vious mild  and  unrecognised  attack  rather  than  to  an 
inherited  immunity.  The  protection  afforded  by  an 
attack  of  the  disease,  however  mild,  is  almost  abso- 


SCARLET  FEVER  225 

lute.  That  is,  second  attacks  are  extremely  rare, 
although  not  unknown. 

The  fact  that  adults  rarely  contract  the  disease  is 
to  a  large  extent  due  to  the  protection  afforded  by 
an  attack  during  infancy  or  childhood.  That  adults 
may  suffer  fatal  attacks  of  the  disease  is  amply 
proved  by  the  mortality  statistics  of  this  and  other 
countries.  The  greatest  number  of  cases,  however, 
occur  between  the  ages  of  two  and  ten  years. 

In  the  United  States  the  mortality  from  this  dis- 
ease during  the  census  year  1900  (6333)  was  some- 
what less  in  proportion  to  the  population  than 
during  the  previous  census  year.  The  proportion 
to  1000  deaths  from  all  causes  was  6.3  in  1900  and 
7.1  in  1890.  These  rates  are  considerably  below 
the  rates  in  England  and  Wales,  where  during  the 
year  1899  scarlet  fever  caused  11.7  in  every  1000 
deaths.  The  mortality  rate  is  higher  in  cities  than 
in  the  country.  The  States  of  New  Jersey  and 
Massachusetts  show  the  highest  mortality  rate  and 
the  State  of  Vermont  the  lowest  (this  applies  only 
to  the  registration  States,  viz.  :  Connecticut,  District 
of  Columbia,  Maine,  Massachusetts,  Michigan,  New 
Hampshire,  New  Jersey,  Rhode  Island,  New  York, 
Vermont). 

Scarlet  fever  is  a  disease  in  which  the  evil  influ- 
ences of  overcrowding  and  insanitary  surroundings 


226  INFECTION  AND  IMMUNITY 

are  not  so  apparent  as  in  many  other  diseases.  In- 
deed some  authors  assert  that  the  children  of  the  rich 
suffer  even  in  greater  proportion  than  those  of  the 
poor.  In  the  United  States  the  mortality  among  the 
coloured  population  is  considerably  less  than  among 
the  whites — 12  deaths  in  1000  from  all  causes  among 
whites  and  2.6  per  1000  among  coloured.  More 
deaths  occur  during  the  winter  than  during  the  sum- 
mer months.  This  is  no  doubt  partly  due  to  the 
unfavourable  influence  of  exposure  to  cold  in  the 
development  of  some  of  the  most  fatal  complications 
which  are  likely  to  occur  during  the  progress  of  the 
disease — nephritis,  pneumonia. 

For  the  prevention  of  scarlet  fever  we  must  de- 
pend entirely  upon  isolation  of  the  sick  and  the  dis- 
infection of  all  infectious  material,  inasmuch  as  no 
method  of  protecting  by  inoculation  is  known,  The 
general  directions  given  with  reference  to  the  disin- 
fection of  the  sick-room  and  its  contents  on  page  220 
apply  equally  to  scarlet  fever.  Special  care  must  be 
taken  with  reference  to  the  sputa  of  the  patient, 
which  should  be  disinfected  by  the  same  methods 
recommended  for  tuberculosis  (p.  171)  and  other 
diseases  in  which  the  infectious  agent  is  present  in 
secretions  from  the  mucous  membrane  of  some  por- 
tion of  the  respiratory  tract. 

The  advantages  attending  the  removal  of  scarlet 


SCARLET  FEVER  227 

fever  patients  to  special  "  contagious-disease  hos- 
pitals "  have  been  amply  demonstrated.  Dr.  Hope, 
Medical  Officer  of  Health  for  the  city  of  Liverpool, 
refers  to  this  in  his  report  for  the  year  1901,  as 
follows  : 

"  Want  of  hospital  accommodation  goes  far  to  explain  the  in- 
crease in  the  number  of  cases  of  scarlet  fever.  The  reduction 
in  the  number  of  cases  of  this  disease,  which  had  been  noted  in 
1900,  ceased  immediately  the  removal  of  patients  to  hospitals  was 
stopped,  although  the  total  removed  was  but  6  %  lower  than  in  the 
previous  year.  This  happened  during  the  annual  cleaning  of 
some  of  the  wards. 

"  When  to  this  is  added  the  economy  to  householders  if  saved 
from  a  complete  disinfection  and  renovation  of  houses,  after 
two  or  three  months'  presence  of  scarlet  fever,  and  the  yet 
greater  value  to  wage-earners  of  being  able  to  go  from  their 
houses  to  continue  their  work,  instead  of  loss  of  time  through  a 
forced  quarantine,  it  will  be  apparent  that  nowhere,  whether  in  a 
large  city  or  in  the  country,  can  there  be  any  question  as  to  the 
advisability  of  having  first  cases  of  scarlet  fever,  like  smallpox, 
removed  to  hospitals  or  a  temporary  building  or  tent,  with,  if 
necessary,  the  mother  to  act  as  nurse." 

In  the  city  of  London,  in  1891,  18,381  cases  of 
scarlet  fever  were  reported  ;  of  these  14,539  (78  %) 
were  treated  in  hospitals,  with  a  mortality  of  542 

(3-73  50- 


CHAPTER  XV 

MEASLES 

DEFORE  the  time  of  Sydenham  (1685)  measles 
^  and  scarlet  fever  were  not,  as  a  rule,  recognised 
as  distinct  diseases  and  both  of  these  eruptive  fevers 
were  commonly  confounded  with  smallpox.  Indeed 
it  not  unfrequently  occurs  even  at  the  present  day 
that  cases  of  smallpox  are  diagnosed  as  measles  at 
the  outset  of  the  attack ;  but  the  development  of 
the  characteristic  eruption  of  smallpox  soon  makes  it 
evident  that  a  serious  mistake  has  been  made.  The 
period  of  incubation  in  measles  is  from  ten  to  twelve 
days,  and  the  eruption  usually  appears  on  the  third 
day  after  the  initial  symptoms  are  developed.  These 
consist  of  fever  and  catarrhal  symptoms,  attended 
with  cough  and  a  watery  discharge  from  the  con- 
gested mucous  membrane  of  the  eyes  and  nose. 

Measles,  like  scarlet  fever,  is  a  disease  which  has 
not  been    materially  influenced   by  modern  sanitary 

measures.     The  sanitary  statistics  of   England  and 

228 


MEASLES  229 

Wales  show  an  increased  mortality  from  this  disease 
during  the  decade  ending  in  1890,  over  the  previous 
ten  years  (2.57  per  1000  deaths  under  five  years  of  age 
in  1871-80  and  3.13  in  1881-90.)  In  the  United 
States  the  total  number  of  deaths  from  measles  re- 
ported during  the  census  year  1900  was  12,866.  The 
number  of  deaths  in  1000  from  all  causes  was  12.9 
while  in  1890  the  proportion  was  u.i,  showing  a 
decided  increase  in  this  country  also.  More  deaths 
occur  in  proportion  to  the  population  in  cities  (18.2 
per  100,000)  than  in  the  country  (9.9  per  100,000). 
The  greatest  mortality  occurs  among  infants  less  than 
a  year  old  (i  52.8  per  100,000)  and  among  young  child- 
ren. After  the  age  of  five  the  mortality  rate  is  greatly 
reduced  (under  five  years  106.5  ;  from  five  to  fourteen 
years  7.4).  The  death-rate  among  the  coloured  popula- 
tion was  somewhat  greater  than  among  native  whites. 
"  The  greatest  proportions  of  deaths  from  measles 
occurred  in  the  South-west  Central  region  (51.7),  the 
South  Mississippi  River  belt  (40.7),  and  the  Southern 
Interior  plateau  (22.7);  and  the  least  in  the  Pacific 
Coast  region  (2.1),  the  Ohio  River  belt  (6.3),  and  the 
Prairie  region  (6.5)"  (Census  Reports,  1900).  The 
mortality  from  measles  is  to  a  large  extent  due  to 
pulmonary  complications,  which  are  especially  liable 
to  occur  in  young  children.  The  influence  of  external 
conditions  in  giving  rise  to  these  fatal  complications 


23o  INFECTION  AND  IMMUNITY 

(broncho-pneumonia,  diphtheria)  is  shown  by  the  fact 
that  the  greatest  mortality  occurs  during  the  months 
of  February,  March,  April,  and  May,  and  the  least 
during  the  summer  and  autumn  months,  also  by  the 
very  low  mortality  of  the  Pacific  Coast  region. 

The  combined  influence  of  an  unfavourable  climate 
and  density  of  population  is  shown  by  the  statistics 
relating  to  the  State  of  Rhode  Island,  which  has  the 
highest  death-rate  from  this  disease  of  any  of  the 
registration  States  (47.6).  The  lowest  rate  in  the  re- 
gistration States  was  in  Vermont  (6.1). 

Patients  having  measles  may  communicate  the  dis- 
ease from  the  very  outset  of  the  attack  and  it  is  prob- 
able that  the  germ  is  present  in  the  abundant 
secretion  from  the  bronchial  and  nasal  mucous  mem- 
branes, as  well  as  in  the  desquamated  epithelium  from 
the  surface  of  the  body  after  the  eruption  has  de- 
veloped. When  convalesence  has  been  established, 
if  the  patient's  body  and  clothing  have  been  disinfected 
he  can  no  longer  communicate  the  disease.  The 
period  during  which  isolation  should  be  insisted  upon, 
to  prevent  the  extension  of  the  disease,  is  about  three 
weeks  from  the  date  of  the  first  appearance  of  the 
eruption.  The  infectious  material  is  not  so  tenacious 
of  vitality  as  in  smallpox  and  scarlet  fever  and  the 
disease  is  not  so  likely  to  be  conveyed  by  means  of 
infected  clothing  and  other  articles  exposed  in  the 


MEASLES  231 

sick-room,  if  an  interval  of  two  or  three  weeks  has 
elapsed  since  infection.  This  fact,  however,  should 
not  lead  to  a  neglect  of  the  usual  measures  of  dis- 
infection heretofore  recommended  (see  p.  220  and  p. 
171).  Free  ventilation  of  the  sick-room,  after  thorough 
scrubbing  of  surfaces  with  hot  water  and  soap  will,  as 
a  rule,  ensure  its  disinfection.  But  it  will  be  prudent 
not  to  allow  susceptible  children  to  enter  such  a  room 
for  at  least  fourteen  days. 

The  following  directions,  published  by  the  Board 
of  Health  of  the  city  of  Glasgow,  set  forth  very 
forcibly  the  importance  of  preventing  the  spread  of 
measles  and  the  fact  that  isolation  of  the  sick  must 
be  relied  upon  as  the  principal  measure  of  prevention: 


"Measles  is  a  dangerous  disease,  one  of  the  most  dangerous 
with  which  a  child  under  five  years  of  age  can  be  attacked.  It 
is  especially  apt  to  be  fatal  to  teething  children.  It  tends  to  kill 
by  producing  inflammation  of  the  lungs.  It  prepares  the  way  for 
consumption.  It  tends  to  maim  by  producing  inflammation  of 
the  eyes  and  ears. 

"  In  Glasgow,  during  the  last  five  years,  measles  has  caused 
three  deaths  for  every  one  which  has  been  caused  by  scarlet 
fever  ;  only  one  infectious  disease  has  been  more  destructive  to 
life,  viz.:  whooping-cough.  Measles  has  carried  off  more  than 
four  times  as  many  persons  as  enteric  fever  (typhoid). 

"It  is  therefore  a  great  mistake  to  look  upon  measles  as  a 
trifling  disease. 

"  The  older  a  child  is  the  less  likely  is  it  to  catch  measles;  and 
if  it  does,  the  less  likely  is  it  to  die. 

"  If  every  child  could  be  protected  from  measles  until  it  had 


232  INFECTION  AND  IMMUNITY 

passed  its  fifth  year,  the  mortality  from  measles  would  be  enorm- 
ously decreased. 

"It  is  therefore  a  great  mistake — because,  as  a  rule,  children 
sooner  or  later  have  measles — to  say  *  The  sooner  the  better,' 
and  to  take  no  means  to  protect  them,  or  even  deliberately  to 
expose  them  to  infection. 

"  It  is  wrong  for  mothers  with  children  in  arms  to  go  into 
houses  where  measles  exists. 

"Every  child  with  measles  ought  at  once  to  be  put  to  bed  and 
kept  warm.  The  mildest  cases  may  be  made  serious  by  a  chill. 
Measles  is  for  this  reason  most  dangerous  in  winter  and  spring. 

"A  case  of  measles  continues  infectious  for  at  least  three 
weeks  after  the  appearance  of  the  rash.  During  that  time  separ- 
ation from  the  healthy  ought  to  be  secured  either  by  removal  of 
the  sick  to  hospital  or  by  isolation  at  home. 

"  Isolation  means  not  merely  a  separate  room  for  the  sick,  but 
the  withdrawal  of  apparently  healthy  children  from  school  (day 
and  Sunday)  and  the  exclusion  of  strange  children  from  the  house. 

"  The  isolation,  as  far  as  possible,  from  other  children  of  all 
children  belonging  to  the  same  family  is  more  necessary  in  the 
case  of  measles  than  of  any  other  infectious  disease,  because  of 
this  peculiarity—/^  days  before  the  rash  comes  out,  the  child  is 
highly  infectious. 

"  School  teachers,  especially,  ought  to  be  familiar  with  the 
appearance  of  children  in  this  stage  of  measles. 

"The  eyes  are  watery,  glistening,  and  sensitive  to  light;  there 
is  a  ringing  cough,  sneezing,  and  running  from  the  nose,  with 
flushed  face;  in  short,  all  the  signs  of  a  bad  cold  in  the  head. 

"  No  child  showing  these  symptoms  ought  to  be  allowed  to  go  to 
school. 

"  Any  child  observed  at  school  with  these  symptoms  ought  to 
be  sent  home  at  once.  Such  children  are  to  be  looked  for  more 
particularly  in  the  Infant  Department. 

"  DR.  J.  B.  RUSSELL. 

"  Sanitary  Office, 

"  Montrose  Street,  Glasgow, 
"January,  1897." 


MEASLES  233 

Second  attacks  of  measles  are  comparatively  rare, 
even  more  so  than  second  attacks  of  smallpox  or 
of  scarlet  fever.  The  apparent  exemption  of  adults 
from  attacks  of  measles  is  largely  if  not  altogether 
due  to  the  fact  that  they  have  usually  suffered  an 
attack  during  childhood.  It  has  been  noticed  that 
regiments  of  soldiers  recruited  in  cities  are  less  sub- 
ject to  measles  than  regiments  raised  in  rural  districts. 
This  is  no  doubt  due  to  the  greater  prevalence  of  the 
disease  among  children  in  cities,  where  few  escape 
attack  during  infancy  or  the  age  of  going  to  school. 

During  a  severe  epidemic  in  the  Faroe  Islands  in 
1 846  scarcely  any  one  escaped  except  those  old  enough 
to  have  passed  through  the  previous  epidemic  in  1 781. 

German  measles  (Rubella)  is  a  distinct  disease 
from  measles,  but  its  specific  character  was  not  gen- 
erally recognised  by  physicians  until  the  last  half  of 
the  nineteenth  century.  An  attack  of  this  disease 
does  not  protect  the  child  from  the  far  more  danger- 
ous disease,  measles. 

The  mortality  from  German  measles  is  practically  nil. 
Its  prevention  is  therefore  of  much  less  importance, 
but  is  to  be  effected  by  the  same  measures,  viz.:  isola- 
tion of  the  sick  and  disinfection  of  all  clothing  and  other 
objects  which  have  been  exposed  in  the  sick-room. 
The  period  of  incubation  in  this  disease  is  quite 
variable,  but  as  a  rule  it  is  longer  than  that  of  measles. 


CHAPTER  XVI 
MALARIAL   FEVERS 

HTHE  discovery  of  the  malarial  parasite  may  justly 
be  considered  one  of  the  greatest  achievements 
of  scientific  research  during  the  nineteenth  century. 
We  owe  it  to  Laveran,  a  surgeon  in  the  French 
army,  who  made  the  discovery  in  1880  while  sta- 
tioned in  Algeria.  His  painstaking  microscopical 
researches  convinced  him  that  the  blood  of  patients 
suffering  from  malarial  fever  contains  living  amoe- 
boid parasites  which  in  one  stage  of  their  develop- 
ment invade  the  red  blood  corpuscles  and  lead  to 
their  destruction.  Subsequent  researches  in  various 
parts  of  the  world  have  made  it  evident  that  this 
blood  parasite  is  in  fact  the  malarial  germ  and  the 
cause  of  the  phenomena  which  characterise  fevers  of 
this  class.  It  has  also  been  demonstrated  that  the 
disease  is  transmitted  to  man  by  mosquitoes  of  the 
genus  Anopheles,  in  the  bodies  of  which  the  para- 
site passes  through  certain  stages  of  development, 

234 


MALARIAL  FEVERS  235 

resulting  in  the  formation  of  a  multitude  of  minute 
spore-like  bodies  which  are  found  in  the  salivary 
glands  of  the  insect. 

Twenty-five  years  ago  the  best-informed  physicians 
entertained  erroneous  views  with  reference  to  the 
nature  of  "malaria"  and  the  cause  of  the  malarial 
fevers.  Observation  had  taught  them  that  there  is 
something  in  the  air  in  the  vicinity  of  marshes  in 
tropical  regions,  and  during  the  summer  and  autumn 
in  semitropical  and  temperate  regions,  which  gives 
rise  to  periodic  fevers  in  those  exposed  in  such 
localities  ;  and  the  usual  inference  was  that  this 
something  was  of  gaseous  form  —  that  it  was  a 
special  kind  of  bad  air  (malaria)  generated  in 
swampy  localities  under  favourable  meteorological 
conditions.  It  was  recognised  at  the  same  time  that 
there  are  other  kinds  of  bad  air,  such  as  the  offensive 
emanations  from  sewers  and  the  products  of  respira- 
tion of  men  and  animals ;  but  the  term  malaria  was 
reserved  for  the  kind  of  bad  air  which  was  supposed 
to  give  rise  to  the  so-called  malarial  fevers.  In  the 
light  of  our  present  knowledge  it  is  evident  that  the 
term  is  a  misnomer.  There  is  no  good  reason  for 
believing  that  the  air  of  swamps  is  any  more  dele- 
terious to  those  who  breathe  it  than  the  air  of  the 
sea-coast  or  that  in  the  vicinity  of  inland  lakes  and 
ponds.  Moreover,  the  stagnant  ponds,  which  are 


236  INFECTION  AND  IMMUNITY 

covered  with  a  "  green  scum  "  and  from  which  bub- 
bles of  gas  are  given  off,  have  lost  all  terrors  for  the 
well-informed  man,  except  in  so  far  as  they  serve  as 
breeding-places  for  mosquitoes  of  the  genus  Ano- 
pheles. The  green  scum  is  made  up  of  harmless 
algae  and  the  gas  which  is  given  off  from  the  mud  at 
the  bottom  of  such  stagnant  pools  is  for  the  most 
part  a  well-known  and  comparatively  harmless  com- 
pound of  hydrogen  and  carbon  —  methane  or  "  marsh 
gas."  In  short,  we  now  know  that  the  air  in  the 
vicinity  of  marshes  is  not  deleterious  because  of  the 
presence  of  any  special  kind  of  bad  air  in  such  local- 
ities but  because  it  contains  mosquitoes  infected  with 
the  malarial  parasite. 

The  discoveries  referred  to,  as  is  usual,  have  had 
to  withstand  the  criticism  of  conservative  physicians, 
who,  having  adopted  the  prevailing  theories  with 
reference  to  the  etiology  of  periodic  fevers,  were 
naturally  skeptical  as  to  the  reliability  of  the  observa- 
tions made  by  Laveran  and  those  who  claimed  to 
have  confirmed  his  discovery.  The  first  contention 
was  that  the  bodies  described  as  present  in  the  blood 
were  not  parasites,  but  deformed  blood  corpuscles. 
This  objection  was  soon  set  at  rest  by  the  demon- 
stration, repeatedly  made,  that  the  intra-corpuscular 
forms  underwent  distinct  amoeboid  movements.  No 
one  witnessing  these  movements  could  doubt  that  he 


MALARIAL  FEVERS  237 

was  observing  a  living  micro-organism.  The  same 
was  true  of  the  extra-corpuscular  flagellate  bodies, 
which  may  be  seen  to  undergo  very  active  move- 
ments, as  a  result  of  which  the  red  blood  corpuscles 
are  violently  displaced  and  the  flagellate  body  itself 
dashes  about  in  the  field  of  view. 

The  first  confirmation  in  this  country  of  Laveran's 
discovery  of  amoeboid  parasites  in  the  blood  of  ma- 
larial-fever patients  was  made  by  myself  in  the  path- 
ological laboratory  of  the  Johns  Hopkins  University 
in  March,  1886.  In  May,  1885,  I  had  visited  Rome  as 
a  delegate  to  the  International  Sanitary  Conference, 
convened  in  that  city  under  the  auspices  of  the 
Italian  Government,  and  while  there  I  visited  the 
Santo  Spirito  Hospital  for  the  purpose  of  witnessing 
a  demonstration,  by  Drs.  Marchiafava  and  Celli,  of 
that  city,  of  the  presence  of  \heplasmodium  malarice 
in  the  blood  of  persons  suffering  from  intermittent 
fever.  Blood  was  drawn  from  the  finger  during  the 
febrile  attack,  from  individuals  to  whom  quinine  had 
not  been  administered.  The  demonstration  was 
entirely  satisfactory,  and  no  doubt  was  left  in  my 
mind  that  I  saw  living  parasitic  micro-organisms  in 
the  interior  of  red  blood  corpuscles  obtained  from 
the  circulation  of  malarial-fever  patients.  The  mo- 
tions were  quite  slow,  and  were  manifested  by  a 
gradual  change  of  outline  rather  than  by  visible 


238  INFECTION  AND  IMMUNITY 

movement.  After  a  period  of  amoeboid  activity  of 
greater  or  less  duration,  the  body  again  assumed  an 
oval  or  spherical  form  and  remained  quiescent  for  a 
time.  While  in  this  form  it  was  easily  recognised, 
as  the  spherical  shape  caused  the  light  passing 
through  it  to  be  refracted,  and  gave  the  impression 
of  a  body  having  a  dark  contour  and  a  central 
vacuole,  but  when  it  was  flattened  out  and  under- 
going amoeboid  changes  in  form  it  was  necessary  to 
focus  very  carefully  and  to  have  a  good  illumination 
in  order  to  see  it.  The  objective  used  was  a  Zeiss's 
one-twelfth  inch  homogeneous  oil  immersion. 

Very  properly,  skepticism  with  reference  to  the 
causal  relation  of  these  bodies  to  the  disease  with 
which  they  are  associated  was  not  removed  by  the 
demonstration  that  they  are  in  fact  blood  parasites, 
that  they  are  present  in  considerable  numbers  during 
the  febrile  paroxysms,  and  that  they  disappear  during 
the  interval  between  these  paroxysms.  These  facts, 
however,  give  strong  support  to  the  inference  that 
they  are  indeed  the  cause  of  the  disease.  This  in- 
ference is  further  supported  by  the  evident  destruc- 
tion of  red  blood  corpuscles  by  the  parasite,  as 
shown  by  the  presence  of  grains  of  black  pigment 
in  the  amoeba-like  micro-organisms  observed  in  these 
corpuscles  and  the  accumulation  of  this  insoluble 
blood  pigment  in  the  liver  and  spleen  of  those  who 


MALARIAL  FEVERS  239 

have  suffered  repeated  attacks  of  intermittent  fever. 
The  enormous  loss  of  red  blood  corpuscles  as  a 
result  of  such  attacks  is  shown  by  the  anaemic  con- 
dition of  the  patient  and  also  by  actual  enumeration. 
According  to  Kelsch,  a  patient  of  vigorous  constitu- 
tion in  the  first  four  days  of  a  quotidian  intermittent 
fever,  or  a  remittent  of  first  invasion,  may  suffer  a 
loss  of  2,000,000  of  red  blood  corpuscles  per  cubic 
millimetre  of  blood,  and  in  certain  cases  a  loss  of 
1,000,000  has  been  verified  at  the  end  of  twenty-four 
hours.  In  cases  of  intermittent  fever  having  a  dura- 
tion of  twenty  to  thirty  days  the  number  of  red 
blood  cells  may  be  reduced  from  the  normal,  which 
is  about  5,000,000  per  cubic  millimetre,  to  1,000,000 
or  even  less. 

In  view  of  this  destruction  of  the  red  blood  cells 
and  the  demonstrated  fact  that  a  certain  number 
at  least  are  destroyed  during  the  febrile  parox- 
ysms by  a  blood  parasite  which  invades  the  cells 
and  grows  at  the  expense  of  the  contained  haemo- 
globin, it  may  be  thought  that  the  causal  relation 
of  the  parasite  should  be  conceded.  But  scien- 
tific conservatism  demands  more  than  this  and  the 
final  proof  has  been  afforded  by  the  experiments 
of  Gerhardt  and  of  Marchiafava  and  Celli  —  since 
confirmed  by  many  others.  This  proof  consists  in 
the  experimental  inoculation  of  healthy  individuals 


240  INFECTION  AND  IMMUNITY 

with  blood  containing  the  parasite  and  the  develop- 
ment of  a  typical  attack  of  periodic  fever  as  a  result 
of  such  inoculation.  After  such  an  inoculation  a 
period  varying  from  four  to  twenty-one  days  elapses 
before  the  occurrence  of  a  febrile  paroxysm.  This  is 
the  so-called  period  of  incubation,  during  which,  no 
doubt,  the  parasite  is  undergoing  multiplication  in 
the  blood  of  the  inoculated  individual.  The  dura- 
tion of  this  period  depends  to  some  extent  upon  the 
quantity  of  blood  used  for  the  inoculation  and  its 
richness  in  parasites.  It  also  depends  upon  the 
particular  variety  of  the  parasite  present,  for  it  has 
been  ascertained  that  there  are  at  least  three  distinct 
varieties  of  the  malarial  parasite  —  one  which  pro- 
duces the  quartan  type  of  fever,  in  which  there  is  a 
paroxysm  every  third  day  and  in  which,  in  experi- 
mental inoculations  made,  the  period  of  incubation 
has  varied  from  eleven  to  eighteen  days ;  one  in 
which  the  paroxysm  occurs  every  second  day  (ter- 
tian), in  which  the  period  of  incubation  is  from 
nine  to  twelve  days;  and  one,  denominated  the 
aestivo-autumnal  type,  in  which  the  period  of  incuba- 
tion rarely  exceeds  five  days. 

The  parasite  associated  with  each  of  these  types 
may  be  recognised  by  an  expert,  and  there  is  no 
longer  any  doubt  that  the  difference  in  type  is 
due  to  the  fact  that  different  varieties  or  "  species " 


MALARIAL  FEVERS  241 

of  the  malarial  parasite  exist,  each  having  a  dif- 
ferent period  of  development.  Blood  drawn  dur- 
ing a  febrile  paroxysm  shows  the  parasite  in  its 
different  stages  of  intra-corpuscular  development. 
The  final  result  of  this  development  is  a  segment- 
ing body,  having  pigment  granules  at  its  centre, 
which  occupies  the  greater  part  of  the  interior 
of  the  red  blood  corpuscle.  The  number  of  seg- 
ments into  which  this  body  divides  differs  in  the 
different  types  of  fever,  and  there  are  other  points 
of  difference  by  which  the  several  varieties  may  be 
distinguished  one  from  the  other,  but  which  it  is  not 
necessary  to  mention  at  the  present  time.  The  im- 
portant point  is  that  the  result  of  the  segmentation 
of  the  adult  parasites  contained  in  the  red  corpuscles 
is  the  formation  of  a  large  number  of  spore-like 
bodies,  which  are  set  free  by  the  disintegration  of 
the  remains  of  the  blood  corpuscles  and  which  con- 
stitute a  new  brood  of  reproductive  elements,  which 
in  their  turn  invade  healthy  blood  corpuscles  and 
effect  their  destruction.  This  cycle  of  development, 
without  doubt,  accounts  for  the  periodicity  of  the 
characteristic  febrile  paroxysms  ;  and,  as  stated,  the 
different  varieties  complete  their  cycle  of  develop- 
ment in  different  periods  of  time,  thus  accounting 
for  the  recurrence  of  the  paroxysms  at  intervals  of 
forty-eight  hours  in  one  type  of  fever  and  of  three 


242  INFECTION  AND  IMMUNITY 

days  in  another  type.  When  a  daily  paroxysm  oc- 
curs, this  is  believed  to  be  due  to  the  alternate  de- 
velopment of  two  groups  of  parasites  of  the  tertian 
variety,  as  it  has  not  been  possible  to  distinguish 
the  parasite  found  in  the  blood  of  persons  suffering 
from  a  quotidian  form  of  intermittent  fever  from 
that  of  the  tertian  form.  Very  often,  also,  the  daily 
paroxysm  occurs  on  succeeding  days  at  a  different 
hour,  while  the  paroxysm  every  alternate  day  is  at 
the  same  hour,  a  fact  which  sustains  the  view  that 
we  have  to  deal,  in  such  cases,  with  two  broods  of 
the  tertian  parasite  which  mature  on  alternate  days. 
In  other  cases  there  may  be  two  distinct  paroxysms 
on  the  same  day  and  none  on  the  following  day, 
indicating  the  presence  of  two  broods  of  tertian 
parasites  maturing  at  different  hours  every  second  day. 
The  hypothesis  that  malarial  infection  results  from 
the  bites  of  mosquitoes  was  advanced  and  ably  sup- 
ported by  Dr.  A.  F.  A.  King,  of  Washington,  D.  C, 
in  a  paper  read  before  the  Philosophical  Society  on 
February  10,  1883,  and  published  in  the  Popular  Sci- 
ence Monthly  in  September  of  the  same  year.  In 
1894  Manson  supported  the  same  hypothesis  in  a 
paper  published  in  the  British  Medical  Journal  (De- 
cember 8th),  and  the  following  year  (1895)  Ross  made 
the  important  discovery  that  when  blood  containing 
the  crescentic  bodies  was  ingested  by  the  mosquito 


MALARIAL  FEVERS  243 

these  crescents  rapidly  underwent  changes  resulting 
in  the  formation  of  motile  filaments,  which  become 
detached  from  the  parent  body  and  continue  to  ex- 
hibit active  movements.  In  1897  Ross  ascertained 
further  that  when  blood  containing  crescents  was 
fed  to  a  particular  species  of  mosquito,  living  pig- 
mented  parasites  could  be  found  in  the  stomach 
walls  of  the  insect.  Continuing  his  researches  with 
a  parasite  of  the  same  class  which  is  found  in  birds, 
and  in  which  the  mosquito  also  serves  as  an  inter- 
mediate host,  Ross  found  that  this  parasite  enters 
the  stomach  wall  of  the  insect,  and,  as  a  result  of  its 
development  in  that  locality,  forms  reproductive 
bodies  (sporozoites),  which  subsequently  find  their 
way  to  the  veneno-salivary  glands  of  the  insect,  which 
is  now  capable  of  infecting  other  birds  of  the  same 
species  as  that  from  which  the  blood  was  obtained 
in  the  first  instance.  Ross  further  showed  that  the 
mosquito  which  served  as  an  intermediate  host  for 
this  parasite  could  not  transmit  the  malarial  parasite 
of  man  or  another  similar  parasite  of  birds  (Jialteri- 
diuni).  These  discoveries  of  Ross  have  been  con- 
firmed by  Grassi,  Koch,  and  others,  and  it  has  been 
shown  that  the  mosquitoes  which  serve  as  inter- 
mediate hosts  for  the  malarial  parasites  of  man  be- 
long to  the  genus  Anopheles,  and  especially  to  the 
species  known  as  Anopheles  claviger. 


244  INFECTION  AND  IMMUNITY 

The  question  whether  malarial  fevers  can  be  con- 
tracted in  any  other  way  than  through  inoculation 
by  infected  mosquitoes,  or  direct  experimental  inocu- 
lation with  the  blood  of  one  suffering  from  malarial 
infection,  has  been  submitted  to  experimental  investi- 
gation, and  the  answer  is  in  the  negative.  Formerly 
it  was  believed  by  many  physicians  that  malarial 
fevers  might  be  contracted  by  drinking  surface  water 
obtained  in  malarious  localities,  but  there  is  no  ex- 
perimental evidence  in  favour  of  this  hypothesis. 
The  first  experiment  of  the  nature  indicated  was 
made  in  the  summer  of  1900,  and  the  results  were 
reported  by  Manson  in  September  of  that  year. 

Five  healthy  individuals  lived  in  a  hut  on  the 
Roman  Campagna  since  early  in  the  month  of  July. 
They  were  protected  against  mosquito  bites  by  mos- 
quito-netting screens  in  the  doors  and  windows  and 
by  mosquito-bars  over  the  beds.  They  went  about 
freely  during  the  daytime,  but  remained  in  their  pro- 
tected hut  from  sunset  to  sunrise.  At  the  time  Man- 
son  made  his  report  all  these  individuals  remained  in 
perfect  health.  It  has  long  been  known  that  labourers 
could  come  from  the  villages  in  the  mountainous  re- 
gions near  the  Roman  Campagna  and  work  during  the 
day,  returning  to  their  homes  at  night,  without  great 
danger  of  contracting  the  fever,  while  those  who  re- 
mained on  the  Campagna  at  night  ran  great  risk  of 


MALARIAL  FEVERS  245 

falling  sick  with  fever,  as  a  result  of  "  exposure  to  the 
night  air."  What  has  already  been  said  makes  it  ap- 
pear extremely  probable  that  the  "  night  air/'/^r  se,  is 
no  more  dangerous  than  the  day  air,  but  that  the  real 
danger  consists  in  the  presence  of  infected  mosquitoes 
of  a  species  which  seeks  its  food  at  night.  As  pointed 
out  by  King,  in  his  paper  already  referred  to,  it  has 
repeatedly  been  claimed  by  travellers  in  malarious 
regions  that  sleeping  under  a  mosquito-bar  is  an 
effectual  method  of  prophylaxis  against  intermittent 
fevers. 

An  experiment  on  a  larger  scale  has  since  been 
made  by  some  medical  officers  of  the  Japanese  army 
on  the  island  of  Formosa,  where  two  companies  of 
soldiers  were  stationed  in  a  very  malarious  locality. 
The  men  of  one  company  were  carefully  protected 
from  the  bites  of  mosquitoes  and  did  not  suffer  attacks 
of  malarial  fever,  while  those  of  the  other  company, 
who  were  not  protected  from  mosquito  bites,  suffered 
severely. 

The  geographic  distribution  of  the  malarial  fevers 
is  coextensive  with  the  conditions  favourable  for  the 
development  of  the  mosquito  which  serves  as  an  inter- 
mediate host  of  the  parasites  to  which  the  disease  is 
due.  Accordingly  we  find  that  these  fevers  prevail  in 
tropical  regions,  where  there  is  abundant  moisture, 
in  all  parts  of  the  world  ;  and  in  temperate  regions, 


246  INFECTION  AND  IMMUNITY 

during  the  summer  months,  wherever  there  are  suit- 
able breeding-places  for  mosquitoes  of  the  genus 
Anopheles. 

The  more  severe  and  fatal  forms  of  malarial  infec- 
tion are  found  especially  in  low-lying  regions  in  the 
tropics.  In  the  United  States  malarial  fevers  are 
common  along  the  Gulf  and  South  Atlantic  coasts, 
and  in  the  valleys  of  rivers  throughout  the  Southern 
and  South-western  States.  There  is  considerable 
malaria  along  the  shores  of  lakes  Ontario  and  Erie, 
but  fevers  of  this  class  are  rare  in  the  vicinity  of  lakes 
Superior  and  Michigan.  The  disease  prevails  in  a 
mild  form  in  some  portions  of  the  States  of  New 
York  and  Pennsylvania  but  is  extremely  rare  in  New 
England  and  is  almost  unknown  on  the  Pacific  Coast. 
Many  localities  in  the  United  States  which  furnished 
numerous  cases  of  malarial  fever  when  first  settled 
have  since  become  comparatively  healthy  as  a  result 
of  agricultural  operations  by  which  marshy  lands  have 
been  drained  and  reclaimed. 

The  seasonal  prevalence  differs  in  different  regions, 
but  in  the  temperate  zone  is  usually  greatest  during 
the  summer  and  early  autumn.  A  considerable  rain- 
fall during  the  spring  and  summer  months  leads  to 
the  formation  of  stagnant  pools  and  marshes  which 
serve  as  breeding-places  for  mosquitoes,  but  an  ex- 
cessive rain-fall,  by  which  swamps  and  ponds  are  kept 


MALARIAL  FEVERS  247 

full  of  water,  is  not  favourable  for  the  multiplication  of 
mosquitoes  and  it  has  long  been  known  that  malarial 
fevers  are  less  prevalent  under  such  circumstances. 
The  total  number  of  deaths  from  malarial  fever 
during  the  census  year  1900  was  14,874  and  the 
proportion  per  1000  deaths  from  all  causes  was 
14.9.  The  proportion  during  the  census  year  1890 
was  considerably  greater  (22.  i).  The  popular  idea 
that  the  negro  is  less  susceptible  to  malarial  fever 
than  the  white  man  does  not  appear  to  receive  sup- 
port from  the  census  returns  as  the  mortality  among 
the  coloured  was  59.8  per  100,000  of  population  and 
among  whites  6.5  per  100,000.  But  it  must  be  re- 
membered that  the  coloured  population  of  the  United 
States  is  located  to  a  much  greater  extent  than  the 
whites  in  the  more  malarious  regions  of  the  country. 
Another  factor  which  probably  vitiates  the  statistics 
to  a  considerable  extent  is  the  fact  that  many  deaths 
ascribed  to  malarial  fever  are  doubtless  due  to  typhoid 
fever.  This  mistake  in  diagnosis  has  frequently  been 
made  in  all  parts  of  the  world  and  is  especially  liable 
to  occur  among  an  ignorant  population.  The  mortal- 
ity from  malarial  fevers  does  not,  however,  fairly  re- 
present the  mischief  accomplished  by  malaria-infected 
mosquitoes. 

The  forms  of  malarial  fever  commonly  encountered 
in  the   United   States  are  rarely  fatal,   especially  if 


248  INFECTION  AND  IMMUNITY 

proper  treatment  is  resorted  to  ( the  administration  of 
quinine).  But  the  infection  is  very  persistent,  re- 
lapses are  frequent,  and  in  malarious  regions  many 
individuals  often  suffer  for  years  from  chronic  mala- 
rial infection  and  finally  succumb  to  some  chronic  or- 
ganic disease  resulting  from  repeated  attacks  of  fever, 
or  from  some  acute  disease  for  which  a  predisposition 
has  been  established  as  a  result  of  continued  ill-health 
and  the  anaemia  which  is  characteristic  of  chronic 
malarial  poisoning.  The  greatest  proportional  num- 
ber of  deaths  from  malarial  fever,  within  the  limits  of 
the  United  States,  during  the  census  year  1900  oc- 
curred in  the  "South  Mississippi  River  belt"  (88.8 
per  1000  deaths  from  all  causes)  ;  the  next  greatest  in 
the  "South  Atlantic  Coast  region"  (61.7)  ;  the  next 
greatest  in  the  "South-west  Central  region  "  (57.9)  ; 
next  in  the  "  Gulf  Coast  region  "  (47.9)  ;  next  in  the 
"Southern  Interior  plateau"  (43.8).  The  least  mor- 
tality occurred  in  the  region  of  the  "  Great  Northern 
Lakes"  (2.2);  next  in  the  "North  Atlantic  Coast 
region"  (2.3);  next  in  the  "Central  Appalachian 
region  "  (2.6)  ;  next  in  the  "  Northeastern  hills  and 
plateaus"  (2.8);  next  in  the  "Pacific  Coast  region" 

(2.9). 

Now  that  we  know  the  life  history  of  the  malarial 
parasite  and  the  manner  by  which  it  gains  access  to 
the  human  body,  the  proper  preventive  measures  are 


MALARIAL  FEVERS  249 

apparent.  In  general  these  consist  in  destroying  the 
breeding-places  of  mosquitoes  when  practicable,  in 
destroying  the  ova  and  larvae  in  marshes  and  pools 
of  stagnant  water,  and  in  avoiding  the  bites  of  the 
insects. 

In  bodies  of  water  containing  minnows  and  other 
small  fish  the  larvae  of  mosquitoes  are  promptly  dis- 
troyed,  as  they  serve  them  as  food.  Frogs  also  feed 
upon  mosquito  larvae.  Mosquitoes  do  not,  as  a  rule, 
deposit  their  eggs  in  running  streams  and  a  perfectly 
smooth  surface  of  water  is  required  for  the  exit  of  the 
adult  mosquito  from  the  puparium.  It  is  said  that 
this  may  be  effectually  prevented  by  agitating  the 
surface  of  the  water  with  a  water-wheel  put  in  motion 
by  a  wind-mill.  There  are  various  temporary  exped- 
ients by  which  the  larvae  may  be  killed  in  the  breed- 
ing-places of  mosquitoes,  but  evidently  the  most 
effectual  remedy  is  to  destroy  the  breeding-places  by 
filling  up  stagnant  pools,  filling  or  draining  marshes, 
and  removing  all  small  receptacles  of  water  from 
the  vicinity  of  dwellings.  Rain-water  barrels,  bottles, 
tin  cans,  street  catch-basins,  etc.,  all  serve  as  breed- 
ing places,  especially  for  mosquitoes  of  the  genus 
Anopheles  which  serve  as  the  intermediate  host  of 
the  malarial  parasite.  As  a  temporary  measure  the 
use  of  petroleum  is  to  be  especially  recommended. 
This  quickly  spreads  out  over  the  surface  of  bodies  of 


250  INFECTION  AND  IMMUNITY 

stagnant  water,  whether  large  or  small,  and  destroys 
the  larvae,  which  are  obliged  to  come  to  the  surface 
from  time  to  time  for  air.  An  ounce  of  oil  is  said  to 
be  sufficient  for  fifteen  square  feet  of  surface,  and  an 
application  of  this  amount  to  be  effective  for  about 
two  weeks. 

The  destruction  of  adult  mosquitoes  near  dwellings 
may  be  to  some  extent  accomplished  by  placing  lighted 
lamps,  in  plates  containing  petroleum,  at  a  little  dis- 
tance from  the  house.  The  mosquitoes  fly  about  the 
lamps  and  many  of  them  are  likely  to  fall  into  the 
petroleum,  which  quickly  kills  them.  The  task  of  kill- 
ing mosquitoes  inside  of  a  house  is,  however,  far  eas- 
ier than  that  of  destroying  those  on  the  outside.  Their 
entrance  should  as  far  as  possible  be  prevented  by 
the  use  of  window  and  door  screens.  Those  which 
pass  these  barriers  should  be  destroyed  by  burning, 
in  the  closed  apartments,  pyrethrum  powder,  or  by 
fumigation  with  formaldehyd  gas  or  sulphur  dioxid 
(formed  by  burning  sulphur).  It  is  especially  import- 
ant that  all  mosquitoes  should  be  killed  in  the 
autumn  in  houses  located  in  malarious  regions. 
Otherwise  they  are  likely  to  hibernate  and  the  females 
will  serve  in  the  spring  to  start  a  new  generation  of 
annoying  and  possibly  dangerous  pests.  They  are  to 
be  found  not  only  in  bedrooms,  but  in  cellars,  kitch- 
ens, closets,  and  attics. 


MALARIAL  FEVERS  251 

For  the  protection  of  individuals  from  the  bites  of 
mosquitoes,  infected  or  otherwise,  a  mosquito-bar  at 
night  and  a  suitable  veil  of  mosquito-netting  in  the 
daytime  will  be  the  most  reliable  resource.  Various 
substances  which  are  obnoxious  to  the  insects  may 
also  be  rubbed  upon  exposed  portions  of  the  body. 
Of  these  oil  of  eucalyptus  is  perhaps  the  most  effica- 
cious. The  following  prescription  is  said  to  serve  a 
useful  purpose  when  applied  to  the  hands  and  face  : 
Ether  and  alcohol,  of  each  five  parts ;  cologne  water 
and  oil  of  eucalyptus,  of  each  ten  parts  ;  tincture  of 
pyrethrum  fifteen  parts.  This  is  to  be  diluted,  be- 
fore it  is  used,  with  four  or  five  parts  of  water  to  one 
of  the  mixture.  An  infusion  of  quassia  is  also  said  to 
be  useful  for  the  same  purpose. 

If  by  the  measures  heretofore  referred  to  the  bites 
of  infected  mosquitoes  can  be  avoided  no  other  pro- 
phylaxis will  be  required.  But  those  who  are  unavoid- 
ably exposed  in  malarious  regions  and  who,  with  all 
possible  precautions,  are  unable  to  escape  the  bites  of 
these  insects  will  do  well  to  take  quinine  in  doses  of 
six  to  ten  grains  during  the  day  at  intervals  of  four  or 
five  days.  This  is  believed  to  be  better  than  a  daily 
dose  of  a  smaller  amount. 


CHAPTER  XVII 

YELLOW  FEVER 

WELLOW  fever  is  an  infectious  disease  which  has 
a  comparatively  restricted  geographic  range. 
Occasional  epidemics  have  occurred  in  North  Amer- 
ica in  every  one  of  our  seaport  cities  as  far  north  as 
Boston  and  on  the  Mississippi  River  as  far  north 
as  St.  Louis,  but  it  has  never  established  itself  as 
an  endemic  disease  within  the  limits  of  the  United 
States.  The  cities  of  Havana,  Vera  Cruz,  and  Rio 
de  Janeiro  have  been  the  principal  foci  of  the  disease 
for  many  years,  and  from  these  cities  it  has  been  car- 
ried to  the  seaports  of  North  and  South  America 
and  of  the  West  Indies.  It  has  also  prevailed  for 
many  years  on  the  west  coast  of  Africa,  which  by 
some  authorities  is  regarded  as  the  original  source  of 
this  pestilential  malady,  while  others  believe  that  it 
already  existed  in  the  West  Indies  at  the  time  of  the 
discovery  of  these  islands.  The  disease  has  never 
reached  the  east  coast  of  Africa,  and  is  unknown  in 

252 


YELLOW  FEVER  253 

Asia.  In  Europe  its  ravages  have  been  restricted  to 
Spain,  to  which  country  it  has  several  times  been 
introduced  by  means  of  ships  coming  from  the  West 
Indies. 

In  the  United  States  several  severe  epidemics  oc- 
curred in  the  city  of  Philadelphia  during  the  latter 
part  of  the  eighteenth  century  (1793,  1797,  1798), 
but  since  that  time  the  ravages  of  the  disease  have, 
for  the  most  part,  been  confined  to  more  southern 
localities. 

During  the  first  sixty  years  of  the  past  century  it 
prevailed  almost  annually  in  one  or  more  of  the 
Southern  seaports  of  the  United  States  and  not 
infrequently  it  extended  its  ravages  to  the  interior 
towns  in  one  or  more  of  the  Southern  States.  So 
frequently  did  it  prevail  during  the  summer  months 
in  New  Orleans  and  Charleston  that  the  permanent 
residents  of  those  cities  commonly  regarded  it  as  a 
disease  of  the  climate  and  a  necessary  evil  which 
it  was  folly  to  attempt  to  combat  by  quarantine 
restrictions. 

In  the  great  epidemic  of  1853,  yellow  fever  pre- 
vailed extensively  in  the  States  of  Florida,  Alabama, 
Louisiana,  Mississippi,  Arkansas,  and  Texas.  The 
epidemic  of  1867  was  limited  to  the  States  of  Louisi- 
ana and  Texas.  Those  States  again  suffered  severely 
in  1873,  and  the  States  of  Florida,  Alabama,  and 


254  INFECTION  AND  IMMUNITY 

Mississippi  were  also  invaded.  A  still  more  extended 
and  deadly  epidemic  occurred  in  1878,  causing  a  mor- 
tality of  15,934  out  of  a  total  number  of  cases  exceed- 
ing 74,000.  In  this  epidemic  the  disease  followed  the 
Mississippi  River  to  the  very  suburbs  of  St.  Louis,  and 
the  State  of  Tennessee  suffered  severely  as  well  as  the 
States  south  of  it.  The  city  of  Memphis  alone  had  a 
mortality  from  the  disease  of  about  five  thousand. 
These  repeated  epidemics  not  only  cost  the  lives  of 
thousands  of  citizens  and  paralysed  business  of  all 
kinds  during  their  prevalence,  but  apprehension  with 
reference  to  the  recurrence  of  the  disease  very  materi- 
ally interfered  with  the  growth  of  many  Southern  cities 
and  retarded  greatly  the  development  of  those  por- 
tions of  the  country  most  liable  to  invasion.  All  this 
is  now  changed  ;  public  health  officials  are  no  longer 
filled  with  apprehension  upon  the  approach  of  sum- 
mer by  the  thought  that  any  ship  arriving  from 
Havana  may  introduce  the  deadly  pestilence  to  our 
shores  ;  commerce  is  no  longer  subjected  to  the  seri- 
ous restrictions  formerly  considered  necessary  for  the 
exclusion  of  the  disease  ;  and  the  public  generally 
have  been  made  aware  that  the  fangs  of  this  threat- 
ening monster  have  been  drawn  by  the  scientific  de- 
monstration of  its  mode  of  attack  and  the  simple 
measures  which  have  been  proved  to  be  effective  in 
preventing  its  propagation. 


YELLOW  FEVER  255 

The  demonstration  that  yellow  fever  is  propagated 
from  man  to  man  by  mosquitoes  of  the  genus  Ste- 
gomyia  was  made  by  a  board  of  medical  officers  of 
the  United  States  army,  which  was  appointed  upon 
the  recommendation  of  the  present  writer,  and  which 
prosecuted  its  researches  in  Cuba  during  the  years 
1 900  and  1 90 1 .  This  board  consisted  of  Major  Walter 
Reed,  Surgeon  U.  S.  A.  ;  Dr.  James  Carroll,  Con- 
tract Surgeon  U.  S.  A.  ;  Dr.  A.  Agramonte,  Contract 
Surgeon  U.  S.  A.  ;  and  Dr.  Jesse  W.  Lazear,  Con- 
tract Surgeon  U.  S.  A. 

In  a  "  Preliminary  Note,"  read  at  the  meeting  of 
the  American  Public  Health  Association,  October  22, 
1 900,  the  board  gave  a  report  of  three  cases  of  yellow 
fever  which  they  believed  to  be  the  direct  result  of 
mosquito  inoculations.  Two  of  these  were  members 
of  the  board,  viz.,  Dr.  Jesse  W.  Lazear  and  Dr. 
James  Carroll,  who  voluntarily  submitted  themselves 
to  the  experiment.  Dr.  Carroll  suffered  a  severe  at- 
tack of  the  disease  and  recovered,  but  Dr.  Lazear 
fell  a  victim  to  his  enthusiasm  in  the  cause  of  science 
and  humanity.  His  death  occurred  on  September 
25th,  after  an  illness  of  six  days'  duration.  About 
the  same  time  nine  other  individuals  who  volunteered 
for  the  experiment  were  bitten  by  infected  mosqui- 
toes— i.  e.,  by  mosquitoes  which  had  previously  been 
allowed  to  fill  themselves  with  blood  from  yellow 


256  INFECTION  AND  IMMUNITY 

fever  patients — and  in  these  cases  the  result  was 
negative.  In  considering  the  experimental  evidence 
thus  far  obtained,  the  attention  of  the  members  of 
the  board  was  attracted  by  the  fact  that  in  the 
nine  inoculations  with  a  negative  result,  "  the  time 
elapsing  between  the  biting  of  the  mosquito  and  the 
inoculation  of  the  healthy  subject  varied  in  seven 
cases  from  two  to  eight  days  and  in  the  remaining 
two  from  ten  to  thirteen  days,  whereas  in  two  of  the 
three  successful  cases  the  mosquito  had  been  kept 
for  twelve  days  or  longer." 

The  inference  drawn  by  Dr.  Reed  and  his  asso- 
ciates, from  the  experiments  thus  far  made,  was  that 
yellow  fever  may  be  transmitted  by  mosquitoes  of  the 
genus  Stegomyia,  but  that  in  order  to  convey  the  infec- 
tion to  a  non-immune  individual  the  insect  must  be 
kept  for  twelve  days  or  longer  after  it  has  filled  itself 
with  blood  from  a  yellow-fever  patient  in  the  earlier 
stages  of  the  disease.  In  other  words,  that  a  certain 
period  of  incubation  is  required  in  the  body  of  the 
insect  before  the  germ  reaches  its  salivary  glands,  and 
consequently  before  it  is  able  to  inoculate  an  individ- 
ual with  the  germs  of  yellow  fever.  This  inference, 
based  upon  experimental  data,  received  support  from 
other  observations,  which  have  been  repeatedly  made, 
with  reference  to  the  introduction  and  spread  of  yel- 
low fever  in  localities  favourable  to  its  propagation. 


YELLOW  FEVER  257 

When  a  case  is  imported  into  one  of  our  Southern 
seaport  cities  from  Havana,  Vera  Cruz,  or  some  other 
endemic  focus  of  the  disease,  an  interval  of  two  weeks 
or  more  occurs  before  secondary  cases  are  developed 
as  a  result  of  such  importation.  In  the  light  of  our 
present  knowledge  this  is  readily  understood.  A 
certain  number  of  mosquitoes  having  filled  themselves 
with  blood  from  this  first  case,  after  an  interval  of 
twelve  days  or  more,  bite  non-immune  individuals 
living  in  the  vicinity,  and  these  individuals,  after  a 
brief  period  of  incubation,  fall  sick  with  the  disease  ; 
being  bitten  by  other  mosquitoes  they  serve  to  trans- 
mit the  disease  through  the  "  intermediate  host "  to 
still  others.  Thus  the  epidemic  extends,  at  first 
slowly  from  house  to  house,  then  more  rapidly,  as 
by  geometrical  progression.  The  results  reported 
by  Dr.  Reed  and  his  associates  have  since  been  fully 
confirmed  by  their  subsequent  experiments  and  by 
independent  investigations  made  in  Cuba  and  also  in 
Brazil. 

Before  the  discovery  that  yellow  fever  is  trans- 
mitted by  mosquitoes,  this  disease  was  generally  re- 
garded as  one  of  the  filth  diseases,  although  there 
were  many  facts  opposed  to  this  view.  In  the  light 
of  our  present  knowledge  we  can  no  longer  class  it 
with  typhoid  fever,  cholera,  bubonic  plague,  and  dys- 
entery, in  which  diseases  the  germ  is  known  to  be 


258  INFECTION  AND  IMMUNITY 

present  in  the  alvine  discharges  of  the  sick,  and  which 
are,  consequently,  well  named  filth  diseases. 

We  now  see  clearly,  however,  why  in  certain  par- 
ticulars relating  to  its  etiology  it  resembles  the  mala- 
rial fevers.  It  is  limited  as  regards  its  prevalence 
to  comparatively  warm  latitudes  or  to  the  summer 
months  in  more  temperate  regions  and  is  dependent, 
to  a  certain  extent,  upon  rainfall  or  the  proximity  of 
standing  water,  because  these  conditions  are  neces- 
sary for  the  propagation  of  mosquitoes. 

It  is  evident  that  in  view  of  our  present  knowledge 
relating  to  the  mode  of  transmission  of  yellow  fever, 
the  preventive  measures  which  have  heretofore  been 
considered  most  important — i.  e.,  isolation  of  the  sick, 
disinfection  of  clothing  and  bedding,  and  municipal 
sanitation — are  either  of  no  avail  or  of  comparatively 
little  value.  It  is  true  that  yellow-fever  epidemics 
have  resulted,  as  a  rule,  from  the  introduction  to  a 
previously  healthy  locality  of  one  or  more  persons 
suffering  from  the  disease.  But  we  now  know  that 
its  extension  did  not  depend  upon  the  direct  contact 
of  the  sick  with  non-immune  individuals  and  that 
isolation  of  the  sick  from  such  contact  is  unnecessary 
and  without  avail.  On  the  other  hand,  complete 
isolation  from  the  agent  which  is  responsible  for  the 
propagation  of  the  disease  is  all-important.  In  the 
absence  of  a  yellow-fever  patient  from  which  to  draw 


YELLOW  FEVER  259 

blood  the  mosquito  is  harmless,  and  in  the  absence  of 
the  mosquito  the  yellow-fever  patient  is  harmless — as 
the  experimental  evidence  now  stands.  Yellow-fever 
epidemics  are  terminated  by  cold  weather,  because 
then  the  mosquitoes  die  or  become  torpid.  The 
sanitary  condition  of  our  Southern  seaport  cities  is  no 
better  in  winter  than  in  summer,  and  if  the  infection 
attached  to  clothing  and  bedding  it  is  difficult  to 
understand  why  the  first  frosts  of  autumn  should 
arrest  the  progress  of  an  epidemic.  But  all  this  is 
explained  now  that  the  mode  of  transmission  has 
been  demonstrated. 

Insanitary  local  conditions  may,  however,  have  a 
certain  influence  in  the  propagation  of  the  disease, 
for  it  has  been  ascertained  that  the  species  of  mos- 
quito which  serves  as  an  intermediate  host  for  the 
yellow-fever  germ  may  breed  in  cesspools  and  sewers, 
as  well  as  in  stagnant  pools  of  water.  If,  therefore, 
the  streets  of  a  city  are  unpaved  and  ungraded  and 
there  are  open  spaces  where  water  may  accumulate 
in  pools,  as  well  as  open  cesspools  to  serve  as  breed- 
ing-places for  Stegomyia  fasciatus,  that  city  will  pre- 
sent conditions  more  favourable  for  the  propagation 
of  yellow  fever  than  it  would  if  well  paved  and 
drained  and  sewered. 

It  will  be  remembered  that  the  malarial  fevers  are 
contracted  as  a  result  of  inoculation  by  mosquitoes 


260  INFECTION  AND  IMMUNITY 

of  the  genus  Anopheles,  and  that  the  malarial  para- 
site has  been  demonstrated  not  only  in  the  blood  of 
those  suffering  from  malarial  infection,  but  also  in 
the  stomach  and  salivary  glands  of  the  mosquito.  If 
the  yellow-fever  parasite  resembled  that  of  the  ma- 
larial fevers  it  would  no  doubt  have  been  discovered 
long  ago.  But  as  a  matter  of  fact,  this  parasite, 
which  we  now  know  is  present  in  the  blood  of  those 
sick  with  the  disease,  has  thus  far  eluded  all  re- 
searches. Possibly  it  is  ultra-microscopic. 

Individuals  of  every  race  and  of  all  ages,  who  are 
exposed  to  infection  for  the  first  time,  during  the 
epidemic  prevalence  of  the  disease,  are  subject  to  be 
attacked.  But  there  is  a  wide  difference  in  the  de- 
gree of  this  susceptibility  among  races,  and  among 
individuals  of  the  same  race. 

It  has  been 'asserted  that  the  negro  race  has  a  con- 
genital immunity  from  yellow  fever,  but  this  is  a 
mistake.  The  susceptibility  of  the  negro  is,  however, 
much  less  than  that  of  the  white  race,  and  among 
those  attacked  the  mortality,  as  a  rule,  is  small. 

Immunity  is  acquired  by  suffering  an  attack  of  the 
disease  ;  this  acquired  immunity  is  not,  however, 
absolute. 

Second  attacks  no  doubt  occasionally  occur,  al- 
though this  has  been  denied  by  some  authors. 

The  proper  measures  of  prophylaxis  are  given  in 


YELLOW  FEVER  261 

the  following  circular,  which  was  submitted  for  my 
approval  by  the  chief  surgeon,  Department  of  Cuba, 
and  was  published  by  the  commanding  general  of 
that  department. 


"  CIRCULAR  )       "  HEADQUARTERS  DEPARTMENT  OF  CUBA, 
"  No.  5.     )  "  Havana,  April  .27,  1901. 

*'  Upon  the  recommendation  of  the  chief  surgeon  of  the  depart- 
ment, the  following  instructions  are  published  and  will  be  strictly 
enforced  at  all  military  posts  in  this  department: 

"The  recent  experiments  made  in  Havana  by  the  Medical 
Department  of  the  Army  having  proved  that  yellow  fever,  like 
malarial  fever,  is  conveyed  chiefly,  and  probably  exclusively,  by 
the  bite  of  infected  mosquitoes,  important  changes  in  the  meas- 
ures used  for  the  prevention  and  treatment  of  this  disease  have 
become  necessary. 

"  i.  In  order  to  prevent  the  breeding  of  mosquitoes  and  to  pro- 
tect officers  and  men  against  their  bites,  the  provisions  of  General 
Orders  No.  6,  Department  of  Cuba,  December  21,  1900,  shall  be 
carefully  carried  out,  especially  during  the  summer  and  fall. 

"  2.  So  far  as  yellow  fever  is  concerned,  infection  of  a  room  or 
building  simply  means  that  it  contains  infected  mosquitoes,  that 
is,  mosquitoes  which  have  fed  on  yellow-fever  patients.  Disin- 
fection, therefore,  means  the  employment  of  measures  aimed  at 
the  destruction  of  these  mosquitoes.  The  most  effective  of  these 
measures  is  fumigation,  with  either  sulphur,  formaldehyd,  or 
insect  powder.  The  fumes  of  sulphur  are  the  quickest  and  most 
effective  insecticide  but  are  otherwise  objectionable.  Formalde- 
hyd gas  is  quite  effective  if  the  infected  rooms  are  kept  closed 
and  sealed  for  two  or  three  hours.  The  smoke  of  insect  powder 
has  also  been  proved  very  useful;  it  readily  stupefies  mosquitoes, 
which  drop  to  the  floor  and  can  then  be  easily  destroyed. 

**  The  washing  of  walls,  floors,  ceilings,  and  furniture  with  dis- 
infectants is  unnecessary. 

"  3.  As  it  has  been  demonstrated  that  yellow  fever  cannot  be 


262  INFECTION  AND  IMMUNITY 

conveyed  by  fomites,  such  as  bedding,  clothing,  effects,  and 
baggage,  they  need  not  be  subjected  to  any  special  disinfection. 
Care  should  be  taken,  however,  not  to  remove  them  from  the 
infected  rooms  until  after  formaldehyd  fumigation,  so  that  they 
may  not  harbour  infected  mosquitoes. 

"  Medical  officers  taking  care  of  yellow-fever  patients  need  not 
be  isolated;  they  can  attend  other  patients  and  associate  with 
non-immunes  with  perfect  safety  to  the  garrison.  Nurses  and 
attendants  taking  care  of  yellow-fever  patients  shall  remain 
isolated,  so  as  to  avoid  any  possible  danger  of  their  conveying 
mosquitoes  from  patients  to  non-immunes. 

"  4.  The  infection  of  mosquitoes  is  most  likely  to  occur  during 
the  first  two  or  three  days  of  the  disease.  Ambulant  cases,  that 
is,  patients  not  ill  enough  to  take  to  their  beds  and  remaining 
unsuspected  and  unprotected,  are  probably  those  most  responsi- 
ble for  the  spread  of  the  disease.  It  is  therefore  essential  that 
all  fever  cases  should  be  at  once  isolated  and  so  protected  that 
no  mosquitoes  can  possibly  get  access  to  them  until  the  nature  of 
the  fever  is  positively  determined. 

"  Each  post  shall  have  a  '  reception  ward  '  for  the  admission 
of  all  fever  cases  and  an  'isolation  ward  '  for  the  treatment  of 
cases  which  prove  to  be  yellow  fever.  Each  ward  shall  be  made 
mosquito-proof  by  wire  netting  over  doors  and  windows,  a  ceil- 
ing of  wire  netting  at  a  height  of  seven  feet  above  the  floor,  and 
mosquito-bars  over  the  beds.  There  should  be  no  place  in  it 
where  mosquitoes  can  seek  refuge,  not  readily  accessible  to  the 
nurse.  Both  wards  can  be  in  the  same  building,  provided  they 
are  separated  by  a  mosquito-tight  partition. 

"  5.  All  persons  coming  from  an  infected  locality  to  a  post  shall 
be  kept  under  careful  observation  until  the  completion  of  five 
days  from  the  time  of  possible  infection,  either  in  a  special  de- 
tention camp  or  in  their  own  quarters;  in  either  case  their  tem- 
perature should  be  taken  twice  a  day  during  this  period  of 
observation,  so  that  those  who  develop  yellow  fever  may  be 
placed  under  treatment  at  the  very  inception  of  the  disease. 

"  6.  Malarial  fever,  like  yellow  fever,  is  communicated  by  mos- 
quito bites  and  therefore  is  just  as  much  of  an  infectious 


YELLOW  FEVER  263 

disease  and  requires  the  same  measures  of  protection  against 
mosquitoes.  On  the  assumption  that  mosquitoes  remain  in  the 
vicinity  of  their  breeding  places,  or  never  travel  far,  the  pre- 
valence of  malarial  fever  at  a  post  would  indicate  want  of  proper 
care  and  diligence  on  the  part  of  the  surgeon  and  commanding 
officer  in  complying  with  General  Orders  No.  6,  Department  of 
Cuba,  1900. 

"  7.   Surgeons  are  again  reminded  of  the  absolute  necessity,  in 
all  fever  cases,  to   keep,  from    the  very   beginning,  a  complete 
chart  of  pulse    and  temperature,    since    such    a   chart   is    their 
best  guide  to  a  correct  diagnosis  and  the  proper  treatment. 
"  BY  COMMAND  OF  MAJOR-GENERAL  WOOD. 

"  H.  L.  SCOTT, 

"Adjutant-General." 

The  practical  execution,  in  the  city  of  Havana,  by 
Major1  Gorgas,  Surgeon  U.  S.  A.,  chief  sanitary  offi- 
cer of  the  city  during  its  occupation  by  our  troops, 
of  the  measures  indicated  in  the  above  circular  was 
attended  with  entire  success.  For  more  than  two 
years  this  city  has  been  entirely  free  from  cases  of 
yellow  fever,  while  for  many  years  prior  to  the  date 
when  Major  Gorgas  inaugurated  his  war  upon  in- 
fected mosquitoes  the  disease  had  prevailed  to  a 
greater  or  less  extent  annually  and  a  certain  number 
of  deaths  had  occurred  every  month  in  the  year. 

1  Now  Colonel  Gorgas,  by  special  act  of  Congress,  as  a  reward  for  his 
services. 


CHAPTER   XVIII 

WOUND  INFECTIONS 

/CERTAIN  of  the  diseases  heretofore  considered 
^-^  may  be  communicated  to  man  by  inoculation 
and  are  occasionally  contracted  by  the  accidental 
inoculation  of  wounds  or  abrasions.  Thus  we  may 
have  a  tubercular  infection  of  the  skin  ("  lupus")  ex- 
tending sometimes  to  adjacent  lymphatic  glands,  or  a 
localised  diphtheritic  process,  upon  any  portion  of 
the  surface  of  the  body.  But  in  the  present  chapter 
we  propose  to  consider  certain  localised  or  general 
infectious  diseases  which  as  a  rule  have  their  origin 
through  the  accidental  introduction  of  pathogenic 
bacteria  into  an  open  wound  or  upon  an  abraded 
surface.  Before  the  days  of  antiseptic  surgery  such 
accidental  inoculations  were  much  more  frequent  than 
at  present.  Erysipelas,  hospital  gangrene,  suppura- 
tion, septicaemia  ("  blood-poisoning "),  and  tetanus 
were  of  frequent  occurrence  and  the  mortality  from 
certain  surgical  operations  which  are  now  almost  free 

264 


WOUND  INFECTIONS  265 

from  risk  was  often  excessive.  These  facts  are  well 
known  to  the  public  and  it  is  also  generally  known 
that  when  a  wound  made  by  the  surgeon,  or  the 
result  of  accident,  suppurates  or  gives  rise  to  fever,  it 
is  because  it  has  become  infected.  The  germs  which 
usually  give  rise  to  wound  infection  have  been  care- 
fully studied  by  bacteriologists  and  are  now  well 
known.  The  two  most  common  species,  which  are 
responsible  to  a  large  extent  for  the  suppuration  of 
wounds,  for  erysipelatous  inflammation,  and  for  "blood- 
poisoning,"  are  widely  distributed  and  are  commonly 
found  upon  the  surface  of  the  body  and  of  mucous 
membranes  in  healthy  persons.  One  of  these  is  a 
micrococcus  which,  when  cultivated  in  artificial  media, 
is  recognised  by  the  fact  that  it  forms  masses  of 
a  golden-yellow  colour.  These  masses  are  made  up 
of  minute  spherical  cells  which  adhere  to  each  other 
in  irregular  grape-like  bunches — hence  the  technical 
name  Staphylococcus  pyogenes  aureus.  The  other  is 
also  a  micrococcus  in  which  the  spherical  cells  are 
united  in  chains,  like  strings  of  pearls.  This  is  called 
Streptococcus  pyogenes.  This  latter  is  also  called  the 
streptococcus  of  erysipelas  because  it  has  been  demon- 
strated to  be  the  cause  of  erysipelatous  inflammations. 
These  two  species  of  pathogenic  bacteria  give  rise 
to  a  great  variety  of  infectious  processes.  Both  are 
found,  either  separately  or  associated,  in  the  pus  of 


266  INFECTION  AND  IMMUNITY 

abscesses,  in  boils  and  carbuncles,  in  suppurating 
wounds,  in  puerperal  fever,  in  peritonitis,  in  suppur- 
ative  disease  of  the  ear,  in  general  blood-poisoning, 
etc. 

As  in  other  infectious  diseases  infection  by  these 
pathogenic  micrococci  (so-called  "  pus  cocci  ")  depends 
upon  three  factors,  viz.  :  the  virulence  of  the  germ  ; 


FlG.  10.     Micrococcus  of  pus-formation  {Staphylococcus  pyogenes  aureus)  ; 
magnified  1000  diameters. 

the  vital  resistance  of  the  tissues  invaded  ;  and  the 
number  of  germs  introduced  into  an  open  wound. 
The  virulence  of  the  germs  is  much  greater  when 
they  come  from  a  suppurating  wound,  from  a  case  of 
erysipelas  or  of  puerperal  fever,  or,  in  short,  from  any 
infectious  process  in  the  body,  than  when  they  come 
from  the  mouth  or  the  surface  of  the  body  where  they 


WOUND  INFECTIONS  267 

have  been  living  a  saprophytic  existence.  Here  it 
may  be  necessary  to  explain  that  a  saprophytic  bac- 
terium is  one  which  exists  independently  of  a  living 
host  and  which  obtains  its  supply  of  nutriment  from 
dead  animal  or  vegetable  material,  while  a  parasitic 
bacterium  is  one  which  invades  the  body  of  a  living 
animal  and  receives  its  nourishment  at  the  expense  of 


FIG.  II.     Micrococcus  of  erysipelas,  etc.  {Streptococcus pyogenes) ;  magnified 
1000  diameters. 

the  tissues  and  body  fluids  of  its  "  host."  But  certain 
bacteria,  like  those  at  present  under  consideration, 
may  live  either  as  saprophytes  or  as  parasites. 

Their  ability  to  effect  a  lodgment  in  the  tissues 
and  multiply  there,  after  having  led  a  saprophytic  life 
for  some  time,  is  favoured  by  a  reduction  in  the  vital 
resisting  power  of  the  individual  as  a  result  of  various 


268  INFECTION  AND  IMMUNITY 

depressing  agencies  —  alcoholism,  insufficient  nourish- 
ment, loss  of  blood,  etc.;  or  by  a  diminished  vital  re- 
sistance at  the  point  of  invasion  as  a  result  of  injury  to 
the  tissues  by  bruising,  by  burns,  by  various  chemical 
agents,  etc. 

When,  however,  these  bacteria  have  been  leading 
a  parasitic  life  for  some  time  they  have  a  greatly 
increased  virulence,  as  manifested  by  their  ability  to 
invade  the  tissues  of  healthy  individuals  whenever 
they  find  a  portal  of  entrance.  Under  such  circum- 
stances, also,  infection  may  result  from  the  introduction 
of  a  very  small  number  of  germs,  whereas  a  compara- 
tively large  number  would  be  required  in  case  the 
micrococci  had  for  some  time  been  leading  a  sapro- 
phytic  existence. 

Fortunately  for  the  human  race  the  blood  serum  of 
healthy  persons  has  the  power  of  destroying  a  limited 
number  of  pathogenic  bacteria  of  a  low  grade  of  viru- 
lence. But  when  these  germs  come  directly  from  the 
seat  of  an  infectious  process,  especially  in  the  case  of 
the  streptococcus,  a  very  small  number  may  give  rise 
to  a  rapidly  extending  and  deadly  blood  infection  - 
for  example  the  blood-poisoning  resulting  from  punc- 
ture of  the  skin  with  a  needle  during  an  autopsy  of  a 
case  of  erysipelas  or  of  puerperal  fever,  or  from  a 
surgical  operation  upon  a  patient  suffering  from  any 
form  of  streptococcus  infection.  Many  pathologists 


WOUND  INFECTIONS  269 

and  surgeons  have  suffered  serious  and  often  fatal 
results  from  such  an  apparently  insignificant  wound. 

Antiseptic  surgery  has  for  its  object  the  destruction 
of  all  bacteria  in  wounds  or  attached  to  objects  which 
are  brought  into  contact  with  wounds,  such  as  the 
hands  and  instruments  of  the  surgeon,  surgical  dress- 
ings, etc.  This  is  accomplished  by  the  use  of  chem- 
ical agents  of  established  germicidal  value,  which 
must  be  used  in  such  a  proportion  as  will  insure  the 
destruction  of  germs,  and  which  will  not  have  an 
injurious  effect  upon  the  vitality  of  the  tissues  and 
the  healing  process.  The  principal  agents  which 
have  been  used  for  this  purpose  are  carbolic  acid  and 
corrosive  sublimate  (mercuric  chloride)  in  solutions 
of  proper  strength.  There  are  certain  objections  to 
the  use  of  either  of  these  agents  in  solutions  strong 
enough  to  promptly  destroy  disease  germs,  especially 
when  applied  to  wounds  of  considerable  magnitude. 
For  this  reason  antiseptic  surgery  has  to  a  considerable 
extent  been  superseded  by  aseptic  surgery^  which  ac- 
complishes the  same  result  without  the  application  of 
chemical  agents  of  any  kind  to  the  wound  surfaces. 
Instruments  and  dressings  are  rendered  sterile  by 
heat,  usually  in  a  steam  steriliser.  The  hands  of  the 
surgeon  and  the  "  field  of  operation  "  are  thoroughly 
scrubbed  with  soap  and  water  and  then  washed  in  an 
antiseptic  solution  to  insure  the  destruction  of  germs 


270  INFECTION  AND  IMMUNITY 

attached  to  the  skin.  Usually  this  is  followed  by 
washing  with  alcohol  and  sterile  water  to  remove  all 
traces  of  the  antiseptic.  Many  surgeons  at  the  pre- 
sent day  prefer  to  wear  india-rubber  gloves  while 
operating,  as  it  has  been  found  by  experience  that 
it  is  a  difficult  matter  to  thoroughly  sterilise  the 
hands.  Such  gloves  are  easily  cleaned  and  sterilised. 
By  the  "  field  of  operation  "  is  meant  the  surface  of 
the  body  in  the  vicinity  of  the  incisions  which  are  to 
be  made  in  any  surgical  operation.  This  surface  is 
cleaned  as  thoroughly  as  possible  and  other  portions 
of  the  body  are  covered  with  a  clean  sheet  or  sterile 
towels.  When  the  operating-room  and  its  fixtures 
are  "  surgically  clean  "  and  all  necessary  precautions 
are  taken  with  reference  to  instruments,  dressings, 
the  surgeon's  hands,  etc.,  an  operation  wound  is  ex- 
pected to  heal  promptly  by  adhesion  of  the  wound 
surfaces,  which  have  been  brought  together  and  re- 
tained by  sutures  or  adhesive  plaster,  and  bandages 
when  necessary. 

Such  wounds  treated  aseptically  rarely  suppurate. 
When  they  do  it  is  because  some  of  the  bacteria 
which  cause  pus  formation  have  found  their  way  into 
the  wound  in  spite  of  the  precautions  taken.  It  is 
more  difficult  to  prevent  suppuration  in  gunshot 
wounds  and  in  extensive  lacerations  resulting  from 
railway  accidents,  etc.  The  bruising  of  the  tissues  in 


WOUND  INFECTIONS  271 

such  cases  renders  them  less  able  to  resist  infection 
and  less  apt  to  unite  by  adhesion. 

It  often  happens,  also,  that  the  wound  is  infected  at 
the  time  it  is  inflicted.  Thus  in  a  gunshot  wound  a 
portion  of  the  clothing  to  which  numerous  germs  are 
attached  may  be  carried  into  the  wound.  Or  the 
bullet  itself  may  be  infected,  although  this  is  no  doubt 
of  rare  occurrence. 

Lacerated  wounds  are  often  inflicted  with  stones, 
pieces  of  wood,  or  other  objects  which  have  dirt 
adhering  to  them,  which  may  contain  various  patho- 
genic bacteria,  and  which  are  liable  to  remain  lodged 
in  the  wound.  Such  a  wound  may  be  cleansed  and 
rendered  aseptic  by  being  thoroughly  washed  with 
sterile  water  (boiled  or  distilled),  or  it  may  be  washed 
with  an  antiseptic  solution  and  treated  with  antisep- 
tic dressings  to  prevent  the  development  of  any  bac- 
teria which  may  chance  to  remain  hidden  away  in  the 
wound. 


CHAPTER  XIX 
TETANUS 

A    FORM  of  wound  infection  of  special  interest,  be- 

cause  of  the  very  serious  results  which  usually 

follow  such  infection,  is  that  by  the  bacillus  of  tetanus, 

which  gives  rise  to  the  disease  commonly  known  as 

lockjaw. 

The  bacillus  of  tetanus  was  discovered  in  1884,  by 
a  student  (Nicholaer)  in  the  laboratory  of  Professor 
Fliigge  of  Gottingen.  Having  introduced  small  quan- 
tities of  garden  earth  under  the  skin  of  mice  and  of 
guinea-pigs,  some  of  these  animals  died  with  all  the 
characteristic  symptoms  of  tetanus.  Subsequent  re- 
searches have  established  the  fact  that  in  temperate 
and  tropical  regions  the  bacillus  of  tetanus  is  widely 
distributed  and  is  commonly  present  in  rich  soil  which 
has  been  manured.  It  is  also  present  in  the  dust  of 
city  streets,  and  there  is  good  reason  to  believe  that 
its  being  found  there  is  due  to  the  fact  that  it  is 

present  in  the  intestinal  contents  of  horses. 

272 


TETANUS 


273 


Formerly  tetanus  was  supposed  to  be  due  to  injury 
to  the  nerves,  and  the  idea  that  it  is  an  infectious 
disease,  due  to  the  introduction  of  a  specific  bacillus 
into  a  wound,  had  not  been  entertained  prior  to  the 
demonstration  that  the  symptoms  which  characterise 
this  disease  may  be  produced  in  the  lower  animals  by 
inoculating  them  with  garden  earth  or  with  a  pure 


FIG.  12.     Bacillus  of  tetanus ;  magnified  1000  diameters.     Spores  are  seen 
at  the  ends  of  some  of  the  bacilli. 

culture  of  the  tetanus  bacillus.  The  nervous  symp- 
toms are  now  known  to  be  due  to  the  fact  that  the 
tetanus  bacillus  produces  a  deadly  poison  (toxin)  which 
has  a  special  affinity  for  the  nervous  tissues.  When 
a  barefooted  boy  steps  upon  a  rusty  nail  and,  as  a  re- 
sult of  the  penetrating  wound  inflicted  by  it,  develops 
tetanus,  this  result  is  not  due  to  the  fact  that  the  nail 

18 


274  INFECTION  AND  IMMUNITY 

was  rusty,  or  that  a  nerve  had  been  injured,  but  to 
the  introduction  of  earth  containing  the  tetanus  ba- 
cillus, which  would  more  readily  adhere  to  the  rough 
surface  of  a  rusty  nail  than  to  a  new  and  clean  one. 
The  nature  of  the  wound  made  is  also  favourable  to  in- 
fection, as  the  bruised  tissues  are  not  likely  to  bleed 
much,  and  the  deep  wound  with  a  narrow  orifice  is 
well  calculated  to  retain  any  foreign  matter  introduced 
at  the  time  the  injury  was  inflicted.  Unlike  the  vari- 
ous pathogenic  bacteria  heretofore  referred  to,  the 
tetanus  bacillus  will  not  grow  in  the  presence  of  oxy- 
gen. It  therefore  cannot  grow  in  open  wounds 
exposed  to  the  air,  and  is  incapable  of  develop- 
ment in  the  blood  of  a  living  animal.  It  differs  in 
another  particular,  also,  viz.,  in  the  formation  of 
"spores,"  which  are  developed  in  the  rods  —  one 
at  the  end  of  each  bacillus.  These  are  spherical, 
highly  refractive  bodies,  which  resist  desiccation,  and 
may  retain  their  vitality  for  months  and  probably 
for  years  when  present  in  surface  soil  or  in  dust. 
A  temperature  of  212°  Fahr.  is  required  for  their 
destruction. 

When  a  needle  is  dipped  into  a  pure  culture  of  the 
tetanus  bacillus,  and  a  mouse  is  inoculated  with  it, 
subcutaneously,  the  animal  falls  sick  within  twenty- 
four  hours  and  dies  of  typical  tetanus  in  two  or  three 
days.  The  tetanic  symptoms  are  first  developed  in 


TETANUS  275 

the  vicinity  of  the  point  of  inoculation.  In  inoculated 
animals,  and  in  tetanus  in  man  resulting  from  acci- 
dental infection,  the  bacillus  may  be  obtained  in  the 
vicinity  of  the  inoculation  wound,  but  is  not  present 
in  the  blood  or  in  the  various  organs  of  the  body. 
The  presence  of  the  deadly  tetanus  toxin  may,  how- 
ever, be  demonstrated  by  injecting  the  blood  of  a 
victim  of  the  disease  into  a  mouse,  which  dies  with 
the  characteristic  tetanic  symptoms  after  such  an  in- 
oculation. The  fatal  dose  of  this  toxin  is  so  small 
that,  according  to  the  Japanese  bacteriologist  Kita- 
sato,  the  amount  of  a  culture,  from  which  all  living 
germs  have  been  removed  by  filtration,  which  is  re- 
quired to  kill  a  mouse  is  not  more  than  one  hundred- 
thousandth  of  a  cubic  centimetre  (o.ooooi  c.c.).  The 
tetanus  poison  is  destroyed  by  five  minutes'  exposure 
to  a  temperature  of  65°  C.  It  is  also  destroyed  by 
exposure  to  direct  sunlight,  but  it  may  be  kept  inde- 
finitely in  a  cool  dark  place.  The  German  chemists, 
Brieger  and  Cohn,  have  obtained  the  toxin  in  a  pre- 
cipitated and  comparatively  pure  state,  in  the  form  of 
yellowish  transparent  scales,  which  are  readily  soluble 
in  water.  They  report  that  this  purified  toxin  will 
kill  a  mouse  in  the  dose  of  0.00000005  gram,  and 
they  estimate  that  0.00023  gram  would  be  a  lethal 
dose  for  a  man.  Comparing  this  with  the  most  deadly 
vegetable  alkaloids  known,  it  is  nearly  six  hundred 


276  INFECTION  AND  IMMUNITY 

times  as  potent  as  atropin  and  one  hundred  and  fifty 
times  as  potent  as  strychnin. 

It  has  long  been  known  that  persons  who  go  bare- 
foot are  more  liable  to  contract  tetanus  than  those 
who  wear  shoes.  This  is  shown  by  the  difference 
in  the  mortality  between  native  soldiers  and  English 
troops  in  India.  Statistics  show  that  the  mortality  is 
higher  among  males  than  among  females.  This,  of 
course,  depends  upon  the  fact  that  they  are  more  out- 
of-doors  and  are  more  likely  to  receive  accidental 
wounds.  It  is  a  rather  remarkable  fact  that  in  the 
United  States  more  deaths  occur  from  tetanus  in 
cities  than  in  the  rural  districts.  This  is  no  doubt 
largely  due  to  the  considerable  number  of  fatal  cases 
of  tetanus  which  occur  among  boys  as  a  result  of 
lacerated  wounds  of  the  hand  made  by  toy  pistols, 
which  are  so  popular  as  a  means  of  celebrating  Inde- 
pendence Day. 

The  use  of  these  pistols  has  now  been  prohibited 
by  several  State  Legislatures.  Dr.  Park  of  Buffalo, 
who  has  given  special  attention  to  the  subject,  re- 
ports that  in  Chicago  during  the  month  of  July,  1881, 
sixty  cases  of  tetanus  occurred  as  a  result  of  injuries 
inflicted  by  toy  pistols.  In  New  York  City  there 
were,  from  the  same  cause,  38  cases  in  1899,  33  cases 
in  1900,  and  27  cases  in  1901. 

During  our  Civil  War  the  total  number  of  cases  of 


TETANUS  277 

tetanus  reported,  as  a  complication  of  gunshot  wounds, 
was  505.  This  is  about  one  case  in  every  five  hundred 
cases  of  gunshot  injury.  The  proportion  has  been 
much  greater  in  wars  conducted  by  other  armies  in 
tropical  countries.  The  total  number  of  deaths  from 
tetanus  in  the  United  States  during  the  census  year 
1900  was  2259,  of  whom  1516  were  males  and  743 
females.  This  includes  the  deaths  from  "  trismus 
neonatorum" — tetanus  of  the  new-born.  Among  the 
poorer  classes  in  southern  localities,  and  especially 
among  the  coloured  population,  tetanus  not  infre- 
quently results  in  the  new-born  from  infection 
through  the  navel.  In  the  registration  area  the  high- 
est mortality  from  tetanus  occurred  in  the  States  of 
Vermont  and  New  Jersey.  That  the  mortality  re- 
ported is  chiefly  among  new-born  infants  is  shown  by 
the  fact  that  of  the  total  number  of  deaths,  1 1 7. 7 
per  100,000  were  among  children  under  one  year 
of  age,  while  the  mortality  between  the  ages  of  five 
to  fourteen  was  only  3.7,  and  between  fifteen  and 
forty-four  only  1.7  per  100,000  of  these  ages.  The 
victims  of  the  toy  pistol  are,  for  the  most  part, 
included  in  the  group  between  the  ages  of  five 
and  fourteen.  The  deaths  below  the  age  of  one 
year,  constituting  a  large  share  of  the  total  num- 
ber, may  justly  be  classed  as  victims  of  dirt.  The 
number  of  deaths  among  the  new-born  was  still 


278  INFECTION  AND  IMMUNITY 

greater  in  the  non-registration  area,  which  includes 
the  Southern  States — viz.,  234.5  per  100,000  infants 
in  cities.  The  death-rate  among  coloured  infants  was 
far  in  excess  of  that  among  whites — in  the  registra- 
tion area:  77.6  whites,  1233.4  coloured,  per  100,000 
children  under  one  year  of  age. 

The  facts  stated  indicate  the  proper  preventive 
measures  in  this  infectious  disease :  the  thorough 
cleansing  of  all  wounds  and  especially  of  penetrating 
and  lacerated  wounds  and  the  use  of  antiseptic  dress- 
ings by  which  the  multiplication  of  the  tetanus  ba- 
cillus will  be  prevented,  if  by  chance  it  has  been 
introduced  ;  the  banishment  of  the  deadly  toy  pistol ; 
cleanliness  and  antiseptic  dressings  of  the  navels  of 
new-born  children  ;  and  last,  but  not  least,  the  educa- 
tion of  the  public  generally  as  to  the  manner  in  which 
wounds  become  infected  with  the  tetanus  bacillus  and 
the  great  danger  attending  such  infection. 


CHAPTER   XX 

HYDROPHOBIA 

A  N OTHER  fatal  form  of  wound  infection  may 
**  result  from  the  bite  of  a  rabid  animal  —  "  hydro- 
phobia." The  germ  of  this  infectious  malady  has  not 
been  discovered,  but  it  has  been  demonstrated  by  ex- 
periment that  it  is  present  in  the  saliva  of  rabid 
animals  and  in  the  nervous  tissues  —  brain  and  spinal 
cord  —  of  men  and  animals  who  succumb  to  the  dis- 
ease. A  considerable  interval  elapses  after  inocula- 
tion before  the  first  symptoms  of  the  disease  are 
manifested.  This  period  of  incubation  varies  greatly 
in  its  duration,  but  is  rarely  less  than  two  weeks  or 
more  than  six  months.  By  far  the  largest  majority 
of  the  cases  are  developed  within  three  months  from 
the  time  the  bite  is  inflicted.  In  the  dog  the  period 
of  incubation  usually  does  not  exceed  two  months. 
When  numerous  and  severe  lacerations  have  been 
inflicted,  especially  if  these  are  upon  the  face,  the 
disease  is  apt  to  develop  at  a  comparatively  early 

279 


280  INFECTION  AND  IMMUNITY 

date.  Bites  upon  the  extremities,  especially  when 
the  teeth  of  the  rabid  animal  have  passed  through  the 
clothing,  by  which  the  virus  is  to  some  extent  re. 
moved,  are  less  likely  to  be  followed  by  an  attack  of 
hydrophobia. 

Among  the  lower  animals  the  following  have  been 
demonstrated  to  be  susceptible  to  rabies  :  dogs,  cats, 
cattle,  sheep,  horses,  goats,  swine,  mice,  rabbits, 
guinea-pigs,  skunks. 

Man  usually  contracts  the  disease  through  the  bites 
of  dogs,  cats,  or  wolves,  and  occasionally  of  skunks. 
A  considerable  proportion  of  those  who  are  bitten  by 
rabid  animals  may  escape  the  disease,  especially  when 
the  bites  are  upon  the  extremities  and  are  not  severe. 
Prompt  cauterisation  of  the  wound  also  has  the  effect 
of  reducing  the  proportion  of  these  attacks. 

The  popular  idea  that  dogs  are  especially  liable  to 
go  mad  in  summer,  during  "the  dog  days,"  appears 
not  to  be  well  founded,  as  it  may  prevail  at  any  season, 
and  dogs  do  not  go  mad  any  more  than  men,  unless 
they  have  been  bitten  by  a  rabid  animal  and  the  virus 
of  the  disease  has  been  introduced  into  the  wound  ; 
or,  as  has  occasionally  happened,  the  infectious  ma- 
terial has  been  introduced  into  an  accidental  wound 
inflicted  in  some  other  way. 

It  has  been  claimed  that  certain  parts  of  the  world 
are  free  from  rabies  and  that  it  does  not  prevail  in 


HYDROPHOBIA  281 

Egypt  or  in  the  city  of  Constantinople,  which  is  noted 
for  the  number  of  its  homeless  dogs.  But  this  is 
denied  by  other  authorities  and  it  is  said  to  have  been 
very  prevalent  in  the  city  of  Constantinople  in  1839. 
Like  other  infectious  diseases  its  prevalence  varies 
greatly  at  different  times  and  depends  to  a  consider- 
able extent  upon  the  measures  taken  to  prevent  its 
extension  —  such  as  the  muzzling  of  dogs  and  the 
destruction  of  those  without  owners. 

In  northern  Europe  rabies  from  the  bite  of  a  mad 
wolf  is  of  not  infrequent  occurrence  and  the  disease  is 
also  occasionally  contracted  as  a  result  of  bites  inflicted 
by  foxes,  jackals,  and  ferrets.  Wild  animals  during 
the  excited  stage  of  the  disease  lose  their  fear  of  man 
and  are  liable  to  run  through  frontier  settlements  and 
military  posts,  and  to  bite  men  and  animals  encoun- 
tered on  their  way. 

A  most  effectual  way  of  resisting  the  spread  of 
rabies  is  by  the  general  muzzling  of  dogs  allowed  to 
run  at  large.  The  results  of  this  preventive  measure 
as  applied  in  Great  Britain  are  given  below.  Accord- 
ing to  official  reports  the  number  of  fatal  cases  of 
rabies  in  1887  was  217;  in  1888,  160;  in  1889,  312- 
This  increase  in  the  number  of  deaths  from  hydro- 
phobia caused  much  alarm  and  led  to  the  enforce- 
ment of  regulations  for  the  muzzling  of  dogs.  As  a 
result  of  this  the  number  of  cases  fell  to  129  in  1890; 


282  INFECTION  AND  IMMUNITY 

79  in  1891,  and  38  in  1892.  There  was  at  this  time 
much  opposition  to  the  muzzling  ordinance  and  it  was 
not  enforced.  As  a  result  of  this  the  number  of  cases 
again  increased  until  in  the  year  1895  it  reached  high- 
water  mark,  672  cases.  Again  the  muzzling  ordinance 
was  enforced,  with  the  result  that  the  number  of  cases 
fell  to  17  in  1898  ;  9  in  1899,  and  zero  in  1900. 

The  number  of  deaths  from  rabies  in  the  United 
States  is  not  shown  in  the  census  reports,  the  cases 
being  no  doubt  included  under  the  heading,  "  Other 
Causes."  In  the  census  of  1900,  33,776  deaths  are 
included  under  this  heading. 

It  is  unfortunate  that  we  have  no  exact  statistics 
with  reference  to  this  disease,  inasmuch  as  its  exist- 
ence has  been  denied  by  certain  members  of  the 
medical  profession. 

It  is  difficult  to  understand  the  mental  operations 
of  those  who  deny  the  existence  of  hydrophobia,  the 
value  of  vaccination,  and  other  well-established  facts, 
except  in  the  case  of  those  who  are  ignorant.  But 
for  certain  minds  the  logic  of  facts  appears  to  have 
no  weight  as  opposed  to  prejudice  and  preconceived 
theories.  That  there  is  an  infectious  disease,  known 
to  us  as  rabies,  which  is  communicated  from  one  ani- 
mal to  others  and  from  rabid  animals  to  man,  by  the 
introduction  of  infectious  material  contained  in  the 
salivary  secretions  into  a  wound — usually  inflicted  by 


HYDROPHOBIA  283 

the  rabid  animal's  teeth — is  as  well  established  as  any 
fact  in  medicine  or  in  history.  But  fortunately  the 
disease  is  rare  and  comparatively  few  physicians  have 
been  called  upon  to  treat  a  case  of  it.  It  is  reported 
that  ninety-one  persons  have  died  of  hydrophobia  in 
the  city  of  Chicago  during  the  past  ten  years. 

The  disease  was  known  to  the  ancients  and  is  very 
clearly  described  by  Celus  (B.C.  21).  As  long  ago 
as  1813  the  French  physicians  Magendie  and  Bouchet 
produced  rabies  in  dogs  by  inoculating  them  with 
saliva  obtained  from  a  man  suffering  from  hydro- 
phobia. But  our  exact  knowledge  of  the  disease 
dates  from  the  researches  of  the  famous  French 
chemist,  Pasteur  (1881  to  1886).  Pasteur  first  an- 
nounced his  success  in  reproducing  rabies  in  suscept- 
ible animals  by  inoculations  with  material  from  the 
nervous  system — brain,  spinal  cord — in  a  communica- 
tion made  to  the  French  Academy  of  Sciences  on 
May  30,  1 88 1.  At  the  same  time  he  reported  his 
success  in  the  discovery  of  "  a  method  for  consid- 
erably shortening  the  period  of  incubation  in  rabies 
and  also  of  reproducing  the  disease  with  certainty." 
This  was  by  inoculations,  made  after  trephining, 
upon  the  surface  of  the  brain,  with  material  obtained 
from  the  brain  of  a  rabid  animal.  Dogs  inoculated 
in  this  way  developed  rabies  in  the  course  of  two 
weeks  and  died  before  the  end  of  the  third  week.  In 


284  INFECTION  AND  IMMUNITY 

a  second  communication  (December  n,  1882)  Pasteur 
reported  his  success  in  communicating  the  disease  by 
intravenous  injections  of  virus  obtained  from  the 
central  nervous  system  of  rabid  animals ;  also  the 
experimental  demonstration  of  the  fact  that  all  forms 
of  rabies  may  be  produced  by  the  same  virus  ;  also, 
that  all  parts  of  the  spinal  cord  of  rabid  animals  are 
virulent,  as  well  as  all  parts  of  the  brain  ;  also  that  an 
animal  (dog)  which  had  recovered  from  a  mild  attack 
after  inoculation  proved  to  be  subsequently  immune, 
and  that  "this  observation  constitutes  a  first  step 
toward  a  discovery  of  the  prophylaxis  of  rabies."  In 
a  subsequent  communication  (May  19,  1884)  Pasteur 
presented  evidence  which  demonstrated  the  fact  that 
by  successive  inoculations  in  monkeys  the  period  of 
incubation  is  prolonged  and  the  virus  of  the  disease 
attenuated ;  that  this  attenuated  (milder)  virus  from 
the  monkey  when  inoculated  into  a  dog  no  longer 
produces  fatal  rabies  ;  and  that  dogs  so  treated  are 
subsequently  immune. 

Having  demonstrated  these  important  facts  Pas- 
teur determined  to  make  a  test  experiment  which 
should  convince  the  scientific  world  of  the  truth  and 
value  of  his  discoveries.  At  his  request  a  commission 
was  appointed  by  the  Minister  of  Public  Instruction 
to  determine  the  efficacy  of  his  method  as  applied 
to  the  protection  of  dogs.  In  his  address  before  the 


HYDROPHOBIA  285 

International  Medical  Congress  at  Copenhagen  (Au- 
gust 11,  1884)  Pasteur  gives  the  following  account 
of  the  results  of  this  test  experiment. 

He  says  that  he  gave  to  the  commission  nineteen 
dogs  which  had  been  rendered  immune  against  rabies 
by  preventive  inoculations.  These  nineteen  dogs  and 
nineteen  control  animals,  obtained  from  the  public 
pound,  without  any  selection,  were  tested  at  the  same 
time.  The  test  was  made  upon  some  of  the  animals  of 
both  series  by  inoculations  with  virulent  material  from 
rabid  animals,  made  upon  the  surface  of  the  brain,  by 
trephining ;  and  upon  others  by  allowing  them  to  be 
bitten  by  rabid  dogs ;  and  upon  still  others  by  intra- 
venous inoculations.  Not  one  of  the  protected  ani- 
mals developed  rabies ;  on  the  other  hand,  three  of 
the  control  animals  out  of  six  bitten  by  mad  dogs 
developed  the  disease  ;  five  out  of  seven  which  re- 
ceived intravenous  inoculations  died  of  rabies  ;  and 
five  which  were  trephined  and  inoculated  upon  the 
surface  of  the  brain  died  of  the  same  disease.  In 
a  subsequent  report  the  commission,  of  which  M. 
Bouley  was  president,  stated  that  twenty-three  dogs, 
which  had  been  protected,  were  bitten  by  mad  dogs 
and  that  all  remained  in  perfect  health,  while  sixty-six 
per  cent,  of  the  control  animals,  bitten  in  the  same 
way,  developed  rabies  within  two  months. 

Evidently  this  method  could  be  applied  upon  a 


286  INFECTION  AND  IMMUNITY 

large  scale  for  the  prevention  of  rabies  among  dogs, 
and  if  these  animals  were  thus  protected,  rabies  would 
soon  become  practically  extinct.  The  method  is  even 
more  reliable  than  vaccination  as  a  protection  against 
smallpox.  But  its  practical  application  on  a  large 
scale  would  be  attended  with  great  difficulties  and 
would,  no  doubt,  be  opposed  by  a  large  proportion 
of  the  owners  of  dogs.  There  has,  therefore,  so  far 
as  I  am  informed,  never  been  any  attempt  to  apply 
this  discovery  of  Pasteur's  in  a  practical  way  for  the 
prevention  of  rabies.  But  these  preliminary  experi- 
ments led  to  the  discovery  that  animals  and  man  may 
be  rendered  immune  to  the  disease  by  protective  in- 
oculations made  after  they  have  been  bitten  by  a 
rabid  animal.  I  shall  not  attempt  to  give  an  account 
of  the  experiments  which  led  Pasteur  to  this  im- 
portant discovery  or  of  the  methods  employed  for 
obtaining  an  attenuated  virus,  but  will  content  myself 
with  a  summary  statement  of  the  results  which  have 
been  attained  in  the  practical  application  of  this 
method  of  prevention. 

It  is  probably  generally  known  that  "  Pasteur  Insti- 
tutes" for  the  treatment  of  persons  bitten  by  rabid 
animals  have  now  been  established  in  all  parts  of  the 
civilised  world.  During  the  year  1891,  1564  persons 
were  inoculated  at  the  Pasteur  Institute  in  Paris 
with  a  total  mortality  of  0.57  per  cent.  In  324  of 


HYDROPHOBIA  287 

these  cases  the  animal  which  inflicted  the  bite  was 
proved  to  be  rabid  by  experimental  inoculations 
made  in  other  animals — with  an  emulsion  of  the 
brain  or  spinal  cord.  This  is  now  generally  recog- 
nised as  a  conclusive  demonstration  that  an  animal, 
or  man,  from  whom  such  virulent  material  has  been 
obtained,  was  a  victim  of  rabies. 

Perdrix  (1890)  in  an  analysis  of  the  results  obtained 
at  the  Pasteur  Institute  in  Paris  calls  attention  to  the 
fact  that  the  mortality  among  those  treated  has  dimin- 
ished each  year  and  ascribes  this  to  improvements 
in  the  method  employed.  In  the  cases  with  severe 
wounds  upon  the  head  and  face  larger  doses  of  the 
virulent  material  are  used  at  more  frequent  intervals. 
Perdrix  gives  the  following  statistics  with  reference 
to  the  location  of  the  bite  as  influencing  the  results 
of  treatment. 

Bitten  upon  the  head,       684;  died,  12  =  1.75  <f> 
Bitten  upon  the  hands,  4396;  died,    9  =  0.2  % 
Bitten  upon  the  limbs,    2839;  died,    5  =  0.17  # 

Recently  the  statistics  of  the  Pasteur  Institute  in 
Paris  for  a  period  of  sixteen  years  (1886  to  1901) 
have  been  published.  During  this  period  112  deaths 
occurred  among  25,986  persons  inoculated — a  mor- 
tality of  0.43  %.  It  is  not  claimed  that  all  of  the 
inoculated  had  been  bitten  by  rabid  animals.  In 
many  cases  it  is  impossible  to  ascertain  whether  the 


288  INFECTION  AND  IMMUNITY 

animal  which  inflicted  the  bite  was  really  mad.  But 
the  cases  in  which  satisfactory  experimental  proof 
has  been  obtained  are  considered  separately  in  the 
statistics  of  the  Pasteur  Institute.  Thus,  in  the  year 
1901,  171  persons  were  treated  who  had  been  bitten 
by  animals  proved  to  be  rabid,  and  among  these 
not  a  single  death  occurred. 


INDEX 


Acquired  immunity,  73 
Alcohol  as  an  antiseptic,  41 
Amoebic  dysentery,  140 
Anopheles,  235 
Anthrax,  23 
Antiseptic,  definition  of,  29 

—  surgery,  269 
Antiseptics,  41 
Antitoxin  of  diphtheria,  198 
Antitoxins,  82 

Aseptic  surgery,  269 
Asiatic  cholera,  1 10 
Attenuation  of  virulence,  64,  78 

Bacilli,  10 

Bacillus  of  bubonic  plague,  101 

—  diphtheria,  193 

—  influenza,  200 

—  leprosy,  182 

—  tetanus,  273 

—  tuberculosis,  160 

—  typhoid  fever,  136 
Bacteria,  37 

—  multiplication  of,  II 

—  structure  of,  13 

—  spores  of,  12 
Bichloride  of  mercury,  61 
Black  death,  91,  93 
Bleaching  powder,  60 
Blood-poisoning,  20 

—  germs  of,  265—269 

Blood   serum,    germicidal   action 
68,  268 
19 


of, 


Breathing  exercises,  176 
Bubonic  plague,  89 

—  bacillus  of,  101 

—  in  Philippine  Islands,  IO2 

—  mortality  from,  94-98 

—  period  of  incubation,  105 

—  prevention  of,  108 

—  protective  inoculations,  107 

Carbolic  acid  as  a  disinfectant,  59 
Caustic  alkalies  as  disinfectants,  58 
Channels  of  infection,  14 
Chicken-pox,  221 
Children,  susceptibility  of,  25 
Chloride  of  lime,  60 
Chlorin  as  a  germicide,  56, 
Chlorinated  lime,  60 
Cholera,  no 

—  germs  of,  120 

—  in  America,  ni-n6 

—  origin  of  epidemics,  117,  118 

—  predisposing  causes,  llS 

—  protective  inoculations,  124 

—  recent  epidemics,  116 
Cholera  germ,  description  of,  120 

—  destruction  of,  118,  122 

—  discovery  of,  I2O 

—  infection  by,  118,  119 
Cholera  infantum,  140 
Citric  acid  as  a  germicide,  57 
Climate  in  treatment  of  consumption, 

177 
Clothing,  disinfection  of,  47 


289 


290 


INDEX 


Clothing,  infection  through,  18 
Coal-tar  products  as  germicides,  59 
Cold,  action  of,  on  bacteria,  46 
Colonies  of  bacteria,  1 1 
Comma  bacillus,  120 
Contagion,  definition  of,  3 
Corrosive  sublimate  as  a  disinfectant, 

61 

Creolin  as  a  disinfectant,  60 
Cresol  as  a  disinfectant,  60 
Culture  experiments,  37 

—  fluids,  38 

Cuspidors   for  consumptive  patients, 
171,  172 

Deodorants,  30 
Desiccation  of  bacteria,  46 
Diphtheria,  191 

—  animals  susceptible  to,  192 

—  antitoxin  of,  198 

—  bacillus  of,  193 

—  disinfection  in,  195 

—  mortality  from,  194 

—  prevention  of,  195 

—  propagation  of,  191 
Diphtheria  bacillus,  193 

—  destruction  of,  195 

—  discovery  of,  192 

—  varieties  of,  192 
Disease  germs.  8 

—  dates  of  discovery,  148 
Disinfectant,  definition  of,  28 
Disinfection,  28 

—  by  gases,  51 

—  evidence  of,  34 

—  in  bubonic  plague,  108 

—  in  cholera,  122,  123 

—  of  bed-linen,  60 

—  of  clothing,  47 

—  of  excreta,  47,  60 

—  of  sick-room,  51-53,  174 

—  of  sputa,  171 

—  tests  of,  32 


Dry  heat  as  a  disinfectant,  44 
Dust,  infection  through,  16,  51 
Dysentery,  140 

—  mortality  from,  141 . 

Ehrlich's  side  chain  theory,  85 
Electric  light,  germicidal  action  of,  49 
Epidemics,  termination  of,  99 
Eruptive  fevers,  17 
Erysipelas,  germ  of,  266,  267 
Excreta,  disinfection  of,  47,  60 

Famine  fever,  151 

Filth  diseases,  103,  126 

Flies,  as  carriers  of  infection,  18 

Fomites,  3 

Formaldehyd  as  a  disinfectant,  54 

Fumigation,  53 

German  measles,  233 
Glanders,  24 

Heat,  disinfection  by,  43 
Hospital  gangrene,  19 
Hydrophobia,  279 

—  mortality  from,  282 

—  Pasteur's  experiments,  283 

—  period  of  incubation,  279 

—  prevention  of,  281 

—  protective  inoculations,  283-288 

—  susceptible  animals,  280 

—  transmission  of,  284 

Immunity,  acquired,  73 

—  due  to  alkalinity  of  blood,  67 

—  due  to  body  temperature,  66 

—  natural,  63 

Infection,  definition  of,  4,  7 

—  general  remarks  upon,  3 
Influenza,  199 

—  bacillus  of,  200 

—  bacillus,  destruction  of,  204 

—  complications  of,  200 

—  epidemics  of,  200-202 


INDEX 


291 


Influenza,  incubation  period,  2O2 

—  mortality  from,  199,  200 

—  predisposing  causes,  202 

—  prevention  of,  203 
Inoculation  for  smallpox,  76 

Lepers,  isolation  of,  189 
Leprosy,  181 

—  bacillus  of,  182 

—  disinfection  in,  190 

—  history  of,  186 

—  in  Great  Britain,  187 

—  in  India  and  China,  187 

—  in  Norway,  188 

—  in  United  States,  189 

—  inoculation  experiments,  182 

—  transmission  of,  186 
Leucocytes,  phagocytic  action  of,  71 
Lime  as  a  disinfectant,  59 

Lye  as  a  disinfectant,  58 
Lysol,  60 

Malaria,  235 
Malarial  fevers,  234 

—  fevers,  geographic  distribution  of, 
245 

—  fevers,  mortality  from,  247 

—  fevers,  period  of  incubation.  240 

—  fevers,  prevention  of,  249-251 

—  fevers,  seasonal  prevalence  of,  246 

—  parasite,  237,  241 

—  parasite,  discovery  of,  234 

—  parasite,  varieties  of,  240-242 
Measles,  228 

—  complications  of,  230 

—  disinfection  in,  230,  231 

—  mortality  from,  229 

—  period  of  incubation,  228 

—  prevention  of,  231 

—  second  attacks,  233 
Membranous  croup,  194 
Metchnikoff's  theory,  72 
Micrococci,  16 


Micrococcus  of  erysipelas,  265,  267 

—  of  pneumonia,  206 

—  of  pneumonia,  discovery  of,  205 

—  of  pneumonia,  where  found,  208 

—  of  puerperal  fever,  266 
Micro-organisms,  8 
Milk,  antitoxins  in,  82 

—  from  tuberculous  cows,  175 
Mineral  acids,  as  germicides,  57 
Mortality  of  armies,  129,  143 
Mosquitoes,  infection  by,  21 

—  malarial  parasite  in,  243 

—  transmission  of   yellow   fever   by, 

255 
Mucous  membrane,  infection  through, 

21 

Natural  immunity,  63 
Oysters,  infection  by,  18 

Pasteur  Institute,    statistics   of,  287, 

288 

Period  of  incubation,  6 
Phagocytosis,  71,  72 
Plasmodium  malariae,  237 
Pneumonia,  205 

—  epidemics  of,  209 

—  in  Chicago,  207 

—  in  United  States,  206 

—  mortality  from,  207 

—  predisposing  causes,  206 

—  prevention  of,  210 

Pocket  flasks  for  consumptives,  172 
Potash  as  a  germicide,  58 
Protective  inoculations,  75-78 

—  inoculations   in    bubonic    plague, 
107,  108 

—  inoculations  in  cholera,  124 

—  inoculations  in  typhoid  fever,  139 
Protophyta,  10 

Protozoa,  10 
Ptomaines,  30 


292 


INDEX 


Puerperal  fever,  germ  of,  266,  267 
Pulmonary     consumption,     mortality 

from,  160-162 
Pure  cultures,  38 

Race  susceptibility,  24 

Rats  as  agents  in  spread  of  plague, 

104 
Relapsing  fever,  145 

—  epidemics  of,  146,  147 

—  germ  of,  148 

—  in  United  States,  147 

—  predisposing  causes,  151 

—  prevention  of,  152 

Salt  as  an  antiseptic,  41 
Sanitoria   in    treatment    of    tubercu- 
losis, 169 

Saprophytes,  86,  267 
Scarlet  fever,  223 

—  history  of,  223 

—  how  communicated,  223 

—  mortality  from,  225 

—  prevention  of,  226 

Second  attacks  of  infectious  diseases, 

73-74 

Septicaemia,  19 
Sewers,  sanitary  value  of,  127 
Ship  fever,  157 
Sick-room,  disinfection  of,  51 
Skin,  infection  through,  21 
Smallpox,  214 

—  disinfection  in,  220 

—  duration  of,  220 

—  germ  of,  219 

—  history  of,  214 

—  mortality  from,  215 

—  second  attacks  of,  74 
Snake  poison,  antitoxin  of,  85 
Soda  as  a  germicide,  59 
Spirilla,  10 

Spirillum  of  cholera,  121 

—  of  relapsing  fever,  149 
Spores,  12,  39 


—  of  tetanus  bacillus,  273,  274 

—  resistance  to  heat,  44 
Sputum,  disinfection  of,  171 
Staphylococcus  pyogenes  aureus,  265 
Steam  as  a  disinfectant,  44 
Streptococcus  pyogenes,  267 
Summer  complaint,  140 

Sulphate  of  copper  as  a  germicide,  62 

—  iron  as  a  germicide,  29 
Sulphur  fumigation,  53,  54 
Sulphurous  acid  as  a  germicide,  58 
Sunlight  as  a  disinfectant,  48 
Susceptibility,  individual,  25 

—  due  to  alcoholism,  68 

—  race,  23 
Surra  disease,  22 

Tetanus,  272 

—  bacillus  of,  273 

—  mortality  from,  276-278 

—  toxin,  273-275 
Texas  fever,  21 

Thermal  death-point  of  bacteria,  45 
Ticks,  infection  by,  21 
Tonsils,  infection  through,  15 
Toy  pistols,  danger  of,  276 
Trichinosis,  19 
Trismus  neonatorum,  277 
Tsetse-fly  disease,  22 
Tubercle  bacillus,  160 

—  destruction  of,  176 

—  discovery  of,  159 

—  in  milk,  175 
Tubercular  joint  disease,  163 
Tuberculosis,  159 

—  communication  of,  159-163 

—  in  Europe,  166 

—  in  New  York  City,  161,  178 

—  influence  of  occupation,  165 
race,  166 

—  mortality  from,  160,  162 

—  of  bowels,  163 

—  predisposing  causes  of,  164 


INDEX 


293 


Tuberculosis,  prevention  of,  170 

—  susceptibility  to,  164 

—  treatment  of,  167 

Typhoid  bacillus,  discovery  of,  136 

—  description  of,  136 

—  destruction  of,  138 

—  in  urine,  135 
Typhoid  fever,  126 

—  bacillus  of,  138 

—  mortality  from,  126-134 

—  preventive  inoculations,  139 

—  second  attacks  of,  74 
Typhus  fever,  154 

—  causes  of,  157 

—  epidemics  of,  154-156 

—  in  United  States,  156 

—  mortality  from,  158 

Uncinaria  Americana,  142 

United  States  Army,  mortality  in,  143 

Urine,  typhoid  bacilli  in,  135 


Vaccination,  76,  221 

—  discovery  of,  218 

—  value  of,  216-218 
Vaccine  virus,  36 

Violet  light,  germicidal  action  of,  49 

Water-born  diseases,  15 
Water  supply,  infection  of,  133 
Whitewash  as  a  disinfectant,  59 
Whooping-cough,  211 

—  mortality  from,  212 

—  prevention  of,  213 
Wound  infections,  19,  264 

Yellow  fever,  252 

—  board  to  investigate,  255 

—  epidemics  in  United   States,   253- 

254 

—  geographic  range,  252-254 

—  prevention  of,  258-265 

—  transmission  of,  255 


The  Science  Series 


Edited  by  Professor  J.  McKEEN  CATTELL,  Columbia  Uni- 
versity, with  the  cooperation  of  FRANK  EVERS  BEDDARD, 
F.R.S.,  in  Great  Britain. 

Each  volume  of  the  series  will  treat  some  department  01 
science  with  reference  to  the  most  recent  advances,  and  will 
be  contributed  by  an  author  of  acknowledged  authority. 
Every  effort  will  be  made  to  maintain  the  standard  set  by  the 
first  volumes,  until  the  series  shall  represent  the  more  im- 
portant aspects  of  contemporary  science.  The  advance  of 
science  has  been  so  rapid,  and  its  place  in  modern  life  has 
become  so  dominant,  that  it  is  needful  to  revise  continually 
the  statement  of  its  results,  and  to  put  these  in  a  form  that  is 
intelligible  and  attractive.  The  man  of  science  can  himself 
be  a  specialist  in  one  department  only,  yet  it  is  necessary  for 
him  to  keep  abreast  of  scientific  progress  in  many  directions. 
The  results  of  modern  science  are  of  use  in  nearly  every  pro- 
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education  and  culture.  A  series  of  scientific  books,  such  as 
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scientific  knowledge. 

The  volumes  will  be  in  octavo  form,  and  will  be  fully  illus- 
trated in  so  far  as  the  subject-matter  calls  for  illustrations. 


G.  P.  PUTNAM'S  SONS,  NEW  YORK  &  LONDON 


THE  SCIENCE  SERIES 


EDITED  BY  J.  MCKEEN  CATTELL,  M.A.,  PH.D.,  AND  F.  E. 
BEDDARD,  M.A.,  F.R.S. 


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8. — Comparative  Physiology  of  the  Brain  and  Comparative  Psy- 
chology. With  special  reference  to  the  Invertebrates.  By  JACQUES 
LOEB,  M.D.,  Professor  of  Physiology  in  the  University  of  Chicago. 
Illustrated.  8°,  $1.75. 

"  No  student  of  this  most  interesting  phase  of  the  problems  of  life  can  afford  to  remain 
in  ignorance  of  the  wide  range  of  facts  and  the  suggestive  series  of  interpretations  which 
Professor  Loeb  has  brought  together  in  this  volume." — JOSEPH  JASTROW,  in  the  Chicago 
Dial. 

9. — The  Stars.  By  Professor  SIMON  NEWCOMB,  U.S.N.,  Nautical  Al- 
manac Office,  and  Johns  Hopkins  University.  8°.  Illustrated.  Net, 
$2.00.  (By  mail,  $2.20.) 

i o.— The  Basis  of  Social  Relations.  A  Study  in  Ethnic  Psychology.  By 
DANIEL  G.  BRINTON,  A.M.,  M.D.,  LL.D.,  Sc.D.,  Late  Professor  of 
American  Archaeology  and  Linguistics  in  the  University  of  Pennsyl- 
vania ;  Author  of  "  History  of  Primitive  Religions,"  "Races  and 
Peoples,"  "  The  American  Race,"  etc.  Edited  by  LIVINGSTON  FAR- 
RAND,  Columbia  University.  8°.  (By  mail,  $1.60.)  Net,  $1.50. 

II. — Experiments  on  Animals.  By  STEPHEN  PAGET.  With  an  Intro- 
duction by  Lord  Lister.  Illustrated.  8°,  net,  $2.00.  (By  mail,  $2.20.) 

12.— Infection  and  Immunity.  With  Special  Reference  to  the  Prevention, 
of  Infectious  Diseases.  By  GEORGE  M.  STERNBERG,  M.D.,  LL.D., 
Surgeon-General  U.  S.  Army  (Retired).  Illustrated.  8°. 

The  following  volumes  are  in  preparation  : 

Meteors  and  Comets.     By  Professor  C.  A.  YOUNG,  Princeton  University. 
The  Measurement  of  the  Earth.     By  Professor  C.  T.  MENDENHALL, 

Worcester  Polytechnic  Institute,  formerly  Superintendent  of  the  U.  S. 

Coast  and  Geodetic  Survey. 

Earthquakes.     By  Major  C.  E.  DUTTON,  U.S.A. 
The  History  of  Science.     By  C.  S.  PEIRCE. 
Recent   Theories   of  Evolution.     By  J.   MARK  BALDWIN,   Princeton 

University. 
The  Reproduction  of  Living  Beings.     By  Professor  MARCUS  HARTOG, 

Queen's  College,  Cork. 

Man  and  the  Higher  Apes.     By  Dr.  A.  KEITH,  F.R.C.S. 
Heredity.     By  J.  ARTHUR  THOMPSON,  School  of  Medicine,  Edinburgh. 
Life  Areas  of  North  America:    A  Study  in  the   Distribution  of 

Animals  and  Plants.      By  Dr.  C.  HART  MERRIAM,   Chief  of  the 

Biological  Survey,  U.  S.  Department  of  Agriculture. 
Age,  Growth,  Sex,  and  Death.     By  Professor  CHARLES  S.  MINOT, 

Harvard  Medical  School. 

History  of  Botany.     By  Professor  A.  H.  GREEN. 
Planetary  Motion.     By  G.  W.  HILL. 
Infection  and  Immunity.     By  GEORGE  M.  STERNBERG,  Surgeon-General, 

U.S.A. 


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